Improve branch list UI (#27319)

1. Put the `"octicon-shield-lock"` into the flex container, then it
doesn't need a separate flex box
2. Remove some unnecessary `gt-df` helpers
3. Make `btn` button has the same flex behavior as `ui button`


![image](https://github.com/go-gitea/gitea/assets/2114189/60ce75f7-7fac-4157-9c42-91c7dee9300e)



![image](https://github.com/go-gitea/gitea/assets/2114189/ea606baf-6f52-41e1-b964-c4840d3b1529)

templates/repo/commit_status.tmpl

@@ -1,5 +1,4 @@
 <!-- make sure this matches the color logic in web_src/js/components/DashboardRepoList.vue -->
-<span class="gt-df">
 {{if eq .State "pending"}}
 	{{svg "octicon-dot-fill" 18 "commit-status icon text yellow"}}
 {{end}}
@@ -12,4 +11,3 @@
 {{if eq .State "failure"}}
 	{{svg "octicon-x" 18 "commit-status icon text red"}}
 {{end}}
-</span>