Clarify "text-align" CSS helpers, fix clone button padding (#25763)

Changes:

* Rename gt-tl/gt-tc/gt-tr to gt-text-left/gt-text-center/gt-text-right
* The gt-ab and gt-br-0 are removed because they are not needed anymore
* Fix the clone dropdown button padding by ":not(.icon)"

Before:

<details>


![image](https://github.com/go-gitea/gitea/assets/2114189/eb030633-622c-4ca7-8e88-ce010d9f51a6)

</details>

After:

<details>


![image](https://github.com/go-gitea/gitea/assets/2114189/64c09403-bf21-439c-88f1-780b34ccab6b)

</details>

Fixes #25758

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

templates/projects/list.tmpl

@@ -1,5 +1,5 @@
 {{if .CanWriteProjects}}
-	<div class="gt-tr">
+	<div class="gt-text-right">
 		<a class="ui small green button" href="{{$.Link}}/new">{{.locale.Tr "repo.projects.new"}}</a>
 	</div>
 	<div class="divider"></div>