docs: update sync vscode instructions

Author: jsjoeio

docs/MAINTAINING.md

@@ -220,8 +220,9 @@ This is currently automated with the release process.
 The VS Code portion of code-server lives under [`coder/vscode`](https://github.com/coder/vscode). To update VS Code for code-server, follow these steps:
 
 1. `git checkout -b vscode-update` - Create a new branch locally based off `main`
-2. `git fetch upstream` - Fetch upstream (VS Code)'s latest `main` branch
-3. `git merge upstream/main` - Merge it locally
+2. `git fetch upstream` - Fetch upstream (VS Code)'s latest branches
+3. `git merge upstream/release/1.64` - Merge it locally
+   1. replace `1.64` with the version you're upgrading to
    1. If there are merge conflicts, fix them locally
 4. Open a PR merging your branch (`vscode-update`) into `main` and add the code-server review team