Make pre-commit hook executable using update-index (#4378)

Task/Issue URL:
https://app.asana.com/0/1205008441501016/1206969865025487/f

### Description
Make pre-commit hook executable using update-index, so executable flag
won't be lost when checking out the file

### Steps to test this PR

_Feature 1_
- [ ] Check .githooks/pre-commit has executable flag set for user, group
and others

### UI changes
No UI changes