fix: "createSlice.extraReducers" warning

[HowardBraham]

Description

Fixes this warning that happens in almost every unit test

console.warn
      The object notation for `createSlice.extraReducers` is deprecated, and will be removed in RTK 2.0. Please use the 'builder callback' notation instead: https://redux-toolkit.js.org/api/createSlice

      15 | import confirmAlertsReducer from './confirm-alerts/confirm-alerts';
      16 |
    > 17 | export default combineReducers({
         |                               ^
      18 |   [AlertTypes.invalidCustomNetwork]: invalidCustomNetwork,
      19 |   [AlertTypes.unconnectedAccount]: unconnectedAccount,
      20 |   activeTab: (s) => (s === undefined ? null : s),

      at buildReducer (node_modules/@reduxjs/toolkit/src/createSlice.ts:356:21)
      at reducer (node_modules/@reduxjs/toolkit/src/createSlice.ts:379:23)
      at node_modules/redux/lib/redux.js:476:24
          at Array.forEach (<anonymous>)
      at assertReducerShape (node_modules/redux/lib/redux.js:474:25)
      at combineReducers (node_modules/redux/lib/redux.js:539:5)
      at Object.<anonymous> (ui/ducks/index.js:17:31)
      at Object.require (ui/store/store.ts:4:1)
      at Object.require (ui/components/multichain/account-list-item/account-list-item.test.js:6:1)

[github-actions]

CLA Signature Action: All authors have signed the CLA. You may need to manually re-run the blocking PR check if it doesn't pass in a few minutes.

[metamaskbot]

Builds ready [18e0261]

• builds: chrome, firefox
• builds (beta): chrome
• builds (flask): chrome, firefox
• builds (test): chrome, firefox
• builds (test-flask): chrome, firefox
• build viz: Build System
• bundle size: Bundle Size Stats
• user-actions-benchmark: User Actions Stats
• storybook: Storybook
• typescript migration: Dashboard
• all CircleCI artifacts
• bundle viz:

  • background: 0, 1, 2, 3, 4, 5, 6, 7, 8
  • common: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14
  • ui: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13
  • content-script: 0
  • offscreen: 0

UI Startup Metrics (1210 ± 58 ms)

Platform	BuildType	Page	Metric	Mean (ms)	Min (ms)	Max (ms)	Std Dev (ms)	P 75 (ms)	P 95 (ms)
Chrome	Browserify	Home	uiStartup	1210	1110	1437	58	1244	1309
			load	1050	952	1186	54	1082	1146
			domContentLoaded	1044	948	1181	55	1074	1141
			domInteractive	16	13	31	3	16	24
			firstPaint	679	73	1155	417	1057	1128
			backgroundConnect	8	4	33	5	8	23
			firstReactRender	20	14	50	6	20	38
			getState	14	6	35	7	19	27
			initialActions	0	0	1	0	0	1
			loadScripts	805	712	935	53	837	907
			setupStore	8	5	24	3	8	12
	Webpack	Home	uiStartup	2214	1785	2596	179	2349	2529
			load	1730	1355	2216	153	1822	1965
			domContentLoaded	1723	1352	2210	152	1819	1954
			domInteractive	15	12	49	8	14	44
			firstPaint	159	71	358	55	175	274
			backgroundConnect	29	10	212	23	34	62
			firstReactRender	153	44	361	107	263	338
			getState	13	5	37	7	18	31
			initialActions	3	1	9	1	4	6
			loadScripts	1718	1350	2208	151	1817	1929
			setupStore	20	7	184	24	22	38
Firefox	Browserify	Home	uiStartup	1361	1181	2001	127	1425	1594
			load	1202	1034	1467	99	1275	1391
			domContentLoaded	1202	1034	1467	99	1275	1391
			domInteractive	107	41	273	37	121	178
			firstPaint	NaN	NaN	NaN	NaN	NaN	NaN
			backgroundConnect	25	13	259	31	22	71
			firstReactRender	25	19	56	9	23	55
			getState	11	5	213	27	8	12
			initialActions	0	0	1	0	0	1
			loadScripts	1181	1017	1385	94	1252	1359
			setupStore	9	4	203	20	7	20
	Webpack	Home	uiStartup	1538	1363	1964	131	1598	1826
			load	1321	1178	1723	117	1391	1571
			domContentLoaded	1321	1178	1723	118	1391	1571
			domInteractive	79	35	137	18	86	123
			firstPaint	NaN	NaN	NaN	NaN	NaN	NaN
			backgroundConnect	21	14	43	5	23	33
			firstReactRender	34	29	45	4	35	42
			getState	9	5	34	5	9	22
			initialActions	1	0	2	1	1	1
			loadScripts	1302	1157	1709	118	1375	1552
			setupStore	8	5	34	4	8	20

Benchmark value 24 exceeds gate value 18 for chrome browserify home p95 backgroundConnect
Benchmark value 2215 exceeds gate value 2192 for chrome webpack home mean uiStartup
Benchmark value 1731 exceeds gate value 1711 for chrome webpack home mean load
Benchmark value 1724 exceeds gate value 1704 for chrome webpack home mean domContentLoaded
Benchmark value 1719 exceeds gate value 1699 for chrome webpack home mean loadScripts
Benchmark value 2529 exceeds gate value 2454 for chrome webpack home p95 uiStartup
Benchmark value 26 exceeds gate value 25 for firefox browserify home mean backgroundConnect
Benchmark value 12 exceeds gate value 11 for firefox browserify home mean getState
Benchmark value 71 exceeds gate value 70 for firefox browserify home p95 backgroundConnect
Sum of mean exceeds: 85ms | Sum of p95 exceeds: 82ms
Sum of all benchmark exceeds: 167ms

Bundle size diffs [🚨 Warning! Bundle size has increased!]

• background: 0 Bytes (0%)
• ui: 0 Bytes (0%)
• common: 14 Bytes (0%)