Simplify helper CSS classes and avoid abuse (#26728)

Removed CSS helper classes (some of them are not useful while some of
them are abused often)

* `gt-db`: in most cases it could be replaced by `gt-df` and the flex
layout should be encouraged. Other cases: either it does need the
`gt-df` (eg: by using `div` directly) or it is an abuse (eg: the warning
message in a form)
* `gt-di`: it doesn't seem useful, or it could be replaced by `gt-dib`
in most cases.
* `gt-dif`: not useful, it could be replaced by `flex-text-inline` or
`gt-df`
* `gt-js`: never used
* All `<i class="icon gt-df gt-ac gt-jc">` could be written as `<i
class="icon">`


## Some UI samples

### Admin Notice


![image](https://github.com/go-gitea/gitea/assets/2114189/d02010d4-dc7d-463f-bc99-dcc9b6e2e2ac)

### Admin Stacktrace


![image](https://github.com/go-gitea/gitea/assets/2114189/4045695c-a8c4-4e37-b720-e77a61b1e965)

### Org Home


![image](https://github.com/go-gitea/gitea/assets/2114189/069f02d0-76ad-4052-8a80-700d7e501d40)

### Org Team Repo


![image](https://github.com/go-gitea/gitea/assets/2114189/dc8d6106-bb6b-4f60-83ac-06cb28df3ab5)

### Release List


![image](https://github.com/go-gitea/gitea/assets/2114189/0845e8a5-d1a9-487a-9d25-3c200ad54c17)


### User Setting Application Token Scope


![image](https://github.com/go-gitea/gitea/assets/2114189/fffbde27-432b-49c6-827e-17b8cd3457ff)

Co-authored-by: Giteabot <teabot@gitea.io>

templates/repo/settings/options.tmpl

@@ -116,7 +116,7 @@
 						<tbody>
 							<tr>
 								<td colspan="4">
-									<span class="text red gt-db gt-py-4 gt-border-secondary-bottom">{{$.locale.Tr "repo.settings.mirror_settings.direction.pull"}}: {{$.locale.Tr "error.occurred"}}</span>
+									<div class="text red gt-py-4 gt-border-secondary-bottom">{{$.locale.Tr "repo.settings.mirror_settings.direction.pull"}}: {{$.locale.Tr "error.occurred"}}</div>
 								</td>
 							</tr>
 						</tbody>