Remove snippet double sync after git action post receive

What does this MR do?

In cd74ff03 we added double snippet sync after a git action. It was implemented because in the former plans, the feature flag will stay and be removed after a couple of releases.

Nevertheless, in order to run the backfilling migration, we need to remove the feature flags. This means that git snippet and db snippet are not going to coexist. Therefore, the git repository will be the single source of trust and we don't need to sync the snippet content in the database.

Does this MR meet the acceptance criteria?

Conformity

• [ ] Changelog entry
• [ ] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content