docs: Update VS Code's outdated Copilot instructions to match other editors (#49823)

Updated outdated instructions for configuring GitHub Copilot to match
those on other editor's migration guides

Before you mark this PR as ready for review, make sure that you have:
- [X] Added a solid test coverage and/or screenshots from doing manual
testing
- [X] Done a self-review taking into account security and performance
aspects
- [X] Aligned any UI changes with the [UI
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)

Release Notes:

- N/A

Co-authored-by: Kunall Banerjee <hey@kimchiii.space>

docs/src/migrate/vs-code.md

@@ -317,18 +317,12 @@ If you’re used to GitHub Copilot in VS Code, you can do the same in Zed. You c
 
 #### Configuring GitHub Copilot
 
-You should be able to sign-in to GitHub Copilot by clicking on the Zeta icon in the status bar and following the setup instructions.
-You can also add this to your settings:
+1. Open Settings with `Cmd+,` (macOS) or `Ctrl+,` (Linux/Windows)
+2. Navigate to **AI → Edit Predictions**
+3. Click **Configure** next to "Configure Providers"
+4. Under **GitHub Copilot**, click **Sign in to GitHub**
 
-```json
-{
-  "features": {
-    "edit_prediction_provider": "copilot"
-  }
-}
-```
-
-To invoke completions, just start typing. Zed will offer suggestions inline for you to accept.
+Once signed in, just start typing. Zed will offer suggestions inline for you to accept.
 
 #### Additional AI Options