Remove temporary indexes for protected ref access levels tables

Remove temporary indexes created to support the migration from !134337 (merged)

After the migration is complete we should be able to drop:

• tmp_idx_protected_branch_push_access_levels_on_id_with_group
• tmp_idx_protected_branch_merge_access_levels_on_id_with_group
• tmp_idx_protected_tag_create_access_levels_on_id_with_group