Update apple.md for latest version of iOS (#2321)

The official iOS app now has a simpler login process for custom instances, directly within the app.

Author: gordinmitya

docs/usage/connect/apple.md

@@ -15,14 +15,10 @@ Install the official Tailscale iOS client from the [App Store](https://apps.appl
 
 ### Configuring the headscale URL
 
-- Open Tailscale and make sure you are _not_ logged in to any account
-- Open Settings on the iOS device
-- Scroll down to the `third party apps` section, under `Game Center` or `TV Provider`
-- Find Tailscale and select it
-  - If the iOS device was previously logged into Tailscale, switch the `Reset Keychain` toggle to `on`
-- Enter the URL of your headscale instance (e.g `https://headscale.example.com`) under `Alternate Coordination Server URL`
-- Restart the app by closing it from the iOS app switcher, open the app and select the regular sign in option
-  _(non-SSO)_. It should open up to the headscale authentication page.
+- Open the Tailscale app
+- Click the account icon in the top-right corner and select `Log in…`.
+- Tap the top-right options menu button and select `Use custom coordination server`.
+- Enter your instance url (e.g `https://headscale.example.com`)
 - Enter your credentials and log in. Headscale should now be working on your iOS device.
 
 ## macOS

hscontrol/templates/apple.go

@@ -27,50 +27,27 @@ func Apple(url string) *elem.Element {
 						elem.Text("App store"),
 					),
 				),
-				elem.Li(nil,
-					elem.Text("Open Tailscale and make sure you are "),
-					elem.I(nil, elem.Text("not ")),
-					elem.Text("logged in to any account"),
-				),
-				elem.Li(nil,
-					elem.Text("Open Settings on the iOS device"),
+				elem.Li(
+					nil,
+					elem.Text("Open the Tailscale app"),
 				),
 				elem.Li(
 					nil,
-					elem.Text(
-						`Scroll down to the "third party apps" section, under "Game Center" or "TV Provider"`,
-					),
+					elem.Text(`Click the account icon in the top-right corner and select "Log in…".`),
 				),
-				elem.Li(nil,
-					elem.Text("Find Tailscale and select it"),
-					elem.Ul(nil,
-						elem.Li(
-							nil,
-							elem.Text(
-								`If the iOS device was previously logged into Tailscale, switch the "Reset Keychain" toggle to "on"`,
-							),
-						),
-					),
+				elem.Li(
+					nil,
+					elem.Text(`Tap the top-right options menu button and select "Use custom coordination server".`),
 				),
 				elem.Li(
 					nil,
 					elem.Text(
 						fmt.Sprintf(
-							`Enter "%s" under "Alternate Coordination Server URL"`,
+							`Enter your instance URL: "%s"`,
 							url,
 						),
 					),
 				),
-				elem.Li(
-					nil,
-					elem.Text(
-						"Restart the app by closing it from the iOS app switcher, open the app and select the regular sign in option ",
-					),
-					elem.I(nil, elem.Text("(non-SSO)")),
-					elem.Text(
-						". It should open up to the headscale authentication page.",
-					),
-				),
 				elem.Li(
 					nil,
 					elem.Text(