[content-init] Don't set a remote tracking branch when creating a local branch for an issue context

[jankeromnes]

Fixes #4366

How to test

Option 1:

• Click here to open an issue in Gitpod
• Make a commit
• Verify that clicking "Push/Pull" in the bottom status bar offers to create a new branch, and doesn't offer to push to origin/main

(⚠️ Don't actually push your commit to the Gitpod repo 😅)

Option 2:

• In any Git clone, run git checkout -B test-branch1 origin/HEAD -- observe that test-branch1 has a remote tracking branch set to origin/main
• Next, run git checkout -B test-branch2 origin/HEAD --no-track -- observe that test-branch2 doesn't have a remote tracking branch (just like when you run git checkout -B test-branch0)
• You can see this in git branch -vv as well

[JanKoehnlein]

LGTM. Thanks for the fast fix