Push rule is not being checked on tag pushes
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### Summary
The "Check whether the commit author is a GitLab user" push rule is not being checked when pushing tags.
### Steps to reproduce
1. Setup a new repository
2. Enable "Check whether the commit author is a GitLab user"
3. Make a commit using a bogus user like ```alice@example.com```
4. Make a tag
5. Push the tag
### Example Project
https://gitlab.com/nuxi/push-rule-bug
### What is the current *bug* behavior?
The tag is accepted because the push rule wasn't checked.
### What is the expected *correct* behavior?
The tag is rejected because the push rule failed. Just like would happen if it was a branch.
### Relevant logs and/or screenshots
Basic setup:
```
$ git config --local user.name Alice
$ git config --local user.email alice@example.com
$ echo "Hey Bob, how you doing?" > README.md
$ git commit -a -m "Message for Bob"
[main 9fb39d1] Message for Bob
1 file changed, 1 insertion(+), 92 deletions(-)
rewrite README.md (100%)
```
We can easily verify that the push rule is working for branches:
```
$ git push origin
Enumerating objects: 5, done.
Counting objects: 100% (5/5), done.
Delta compression using up to 2 threads
Compressing objects: 100% (1/1), done.
Writing objects: 100% (3/3), 264 bytes | 264.00 KiB/s, done.
Total 3 (delta 0), reused 0 (delta 0), pack-reused 0
remote: GitLab: Author 'alice@example.com' is not a member of team
To gitlab.com:nuxi/push-rule-bug.git
! [remote rejected] main -> main (pre-receive hook declined)
error: failed to push some refs to 'gitlab.com:nuxi/push-rule-bug.git'
```
But if you make a tag and push it, the push is accepted:
```
$ git tag moof
$ git push origin moof
Enumerating objects: 5, done.
Counting objects: 100% (5/5), done.
Delta compression using up to 2 threads
Compressing objects: 100% (1/1), done.
Writing objects: 100% (3/3), 264 bytes | 264.00 KiB/s, done.
Total 3 (delta 0), reused 0 (delta 0), pack-reused 0
To gitlab.com:nuxi/push-rule-bug.git
* [new tag] moof -> moof
```
### Output of checks
This bug happens on GitLab.com (which currently runs 14.10.0-pre)
I originally discovered it on a private instance running 14.3.2-ee.
### Possible fixes
Unknown.
issue