Fix admin notices (#10480)

Signed-off-by: jolheiser <john.olheiser@gmail.com>

routers/routes/routes.go

 		m.Group("/notices", func() {
 			m.Get("", admin.Notices)
 			m.Post("/delete", admin.DeleteNotices)
-			m.Get("/empty", admin.EmptyNotices)
+			m.Post("/empty", admin.EmptyNotices)
 		})
 	}, adminReq)
 	// ***** END: Admin *****

templates/admin/notice.tmpl

 								<th></th>
 								<th colspan="5">
 									<div class="ui right">
-										<a class="ui red small button" href="{{AppSubUrl}}/admin/notices/empty">{{.i18n.Tr "admin.notices.delete_all"}}</a>
+										<form method="post" action="{{AppSubUrl}}/admin/notices/empty">
+											{{.CsrfTokenHtml}}
+											<button type="submit" class="ui red small button">{{.i18n.Tr "admin.notices.delete_all"}}</button>
+										</form>
 									</div>
 									<div class="ui floating upward dropdown small button">
 										<span class="text">{{.i18n.Tr "admin.notices.actions"}}</span>

web_src/less/_admin.less

             }
         }
 
-        form button[type='submit'] {
+        form tbody button[type='submit'] {
             padding: 5px 8px;
         }
     }