gruvbox: `version_control_` -> `version_control.` (#26665)

Missed this in PR #26606 

Before:

![CleanShot 2025-03-13 at 08 58
59@2x](https://github.com/user-attachments/assets/021df4b1-5a70-4fae-a109-9b8bb35949e3)

After:

![CleanShot 2025-03-13 at 08 59
22@2x](https://github.com/user-attachments/assets/01dca26d-77ec-4a54-8b7c-aa2fb160ff7d)

Release Notes:

- theme: Fixed an issue where version control colors weren't applying
correctly. (again)