[gitlab]: Fix selector for sidebar time-tracker class

[glensc]

🌟 What does this PR do?

Restore the button that has been gone for a while:

I was reported internally by our project manager to your project manager, but no action came out of it, even the issue I had to create myself half year later:

• Restore Additional toggl button to timetracking block #2140

and yet no action to that either, so here's my attempt to do your job what we pay you.

🐛 Recommendations for testing

All changes should be tested across Chrome and Firefox.

📝 Links to relevant issues or information

Fixes #2140

[glensc]

CI fails with:

All files src/content/gitlab.js
Error: File src/content/gitlab.js has a faulty header. Check CONTRIBUTING.md
Error: Process completed with exit code 1.

• https://github.com/glensc/toggl-button/actions/runs/3959712728/jobs/6782893818

that error message is not useful, what exactly should I check from there? I searched for word "header" and found 0 matches:

$  grep -ci header docs/CONTRIBUTING.md
0

EDIT: proposed fix: #2158

[Alissonsz]

LGTM! It fixes the problem.
Sorry for the big waiting time for the review, and thanks for the help and patience 😄