fix: grammar in a release API error message (#7565)

This is small bug fix to correct the API's response description.

Currently returns "Release is has no Tag"
I think would read better as "Release has no Tag"

I have not added a test as it's a trivial change, however it's possible that consumers might be looking for that particular string.

## Checklist

The [contributor guide](https://forgejo.org/docs/next/contributor/) contains information that will be helpful to first time contributors. There also are a few [conditions for merging Pull Requests in Forgejo repositories](https://codeberg.org/forgejo/governance/src/branch/main/PullRequestsAgreement.md). You are also welcome to join the [Forgejo development chatroom](https://matrix.to/#/#forgejo-development:matrix.org).

### Tests

- I added test coverage for Go changes...
  - [ ] in their respective `*_test.go` for unit tests.
  - [ ] in the `tests/integration` directory if it involves interactions with a live Forgejo server.
- I added test coverage for JavaScript changes...
  - [ ] in `web_src/js/*.test.js` if it can be unit tested.
  - [ ] in `tests/e2e/*.test.e2e.js` if it requires interactions with a live Forgejo server (see also the [developer guide for JavaScript testing](https://codeberg.org/forgejo/forgejo/src/branch/forgejo/tests/e2e/README.md#end-to-end-tests)).

### Documentation

- [ ] I created a pull request [to the documentation](https://codeberg.org/forgejo/docs) to explain to Forgejo users how to use this change.
- [x] I did not document these changes and I do not expect someone else to do it.

### Release notes

- [x] I do not want this change to show in the release notes.
- [ ] I want the title to show in the release notes with a link to this pull request.
- [ ] I want the content of the `release-notes/<pull request number>.md` to be be used for the release notes instead of the title.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/7565
Reviewed-by: Earl Warren <earl-warren@noreply.codeberg.org>
Co-authored-by: David Davies-Payne <d2p@me.com>
Co-committed-by: David Davies-Payne <d2p@me.com>

routers/api/v1/repo/release.go

@@ -267,7 +267,7 @@ func CreateRelease(ctx *context.APIContext) {
 		}
 	} else {
 		if !rel.IsTag {
-			ctx.Error(http.StatusConflict, "GetRelease", "Release is has no Tag")
+			ctx.Error(http.StatusConflict, "GetRelease", "Release has no Tag")
 			return
 		}