Fix layouts of admin table / adapt repo / email test (#24370)

Ref:
https://github.com/go-gitea/gitea/pull/24315#pullrequestreview-1403034993

And fix the incorrect layout for "dasbboard", the "form" shouldn't
follow `<h4 class="ui top attached header">`, so move it to inner.

Diff with ignoring spaces:
https://github.com/go-gitea/gitea/pull/24370/files?diff=unified&w=1

A known bug: the adapt/delete button doesn't work due to a historical
messy logic, will fix it in next PR (#24374)

![image](https://user-images.githubusercontent.com/2114189/234754656-d160b098-b8d4-4783-962a-27d5c764863c.png)

![image](https://user-images.githubusercontent.com/2114189/234762327-3e77e2e4-a156-4498-8a8b-092e14cf9204.png)

![image](https://user-images.githubusercontent.com/2114189/234767811-74b7272c-e40c-4850-8e3c-499e3b53b827.png)

![image](https://user-images.githubusercontent.com/2114189/234761247-e6aad889-dcad-443c-948f-2d44df68725b.png)

templates/admin/repo/list.tmpl

@@ -1,4 +1,4 @@
-{{template "admin/layout_head" (dict "ctxData" . "pageClass" "admin user")}}
+{{template "admin/layout_head" (dict "ctxData" . "pageClass" "admin")}}
 	<div class="admin-setting-content">
 		<h4 class="ui top attached header">
 			{{.locale.Tr "admin.repos.repo_manage_panel"}} ({{.locale.Tr "admin.total" .Total}})