Fix mjs import for Turbopack test (#56354)

Turbopack currently supports fully-specified `.mjs` imports. Double
check with @sokra to verify if this is correct.

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Author: timneutkens

test/e2e/app-dir/set-cookies/app/api/app/edge/route.js

@@ -1,6 +1,6 @@
 export const runtime = 'edge'
 
-import cookies from '../../../../cookies'
+import cookies from '../../../../cookies.mjs'
 
 export async function GET() {
   const headers = new Headers()

test/e2e/app-dir/set-cookies/app/api/app/experimental-edge/route.js

@@ -1,6 +1,6 @@
 export const runtime = 'experimental-edge'
 
-import cookies from '../../../../cookies'
+import cookies from '../../../../cookies.mjs'
 
 export async function GET() {
   const headers = new Headers()

test/e2e/app-dir/set-cookies/app/api/app/node/route.js

@@ -1,4 +1,4 @@
-import cookies from '../../../../cookies'
+import cookies from '../../../../cookies.mjs'
 
 export async function GET() {
   const headers = new Headers()

test/e2e/app-dir/set-cookies/pages/api/pages/edge.js

@@ -1,6 +1,6 @@
 export const runtime = 'edge'
 
-import cookies from '../../../cookies'
+import cookies from '../../../cookies.mjs'
 
 export default async function handler() {
   const headers = new Headers()

test/e2e/app-dir/set-cookies/pages/api/pages/experimental-edge.js

@@ -1,4 +1,4 @@
-import cookies from '../../../cookies'
+import cookies from '../../../cookies.mjs'
 
 export const runtime = 'edge'
 

test/e2e/app-dir/set-cookies/pages/api/pages/node.js

@@ -1,4 +1,4 @@
-import cookies from '../../../cookies'
+import cookies from '../../../cookies.mjs'
 
 export default async function handler(_req, res) {
   res.appendHeader('set-cookie', cookies)