Improve commit date in commit graph (#24399)

The commit date time is based on server's time zone not user's local
time zone.

Before:

![image](https://user-images.githubusercontent.com/18380374/235074112-cc1e032f-6b43-4876-a1bc-dd48b393866b.png)

After:

![image](https://user-images.githubusercontent.com/18380374/235074056-329811e8-3e81-4b55-b5a1-580ac22b6d72.png)

templates/repo/graph/commits.tmpl

@@ -71,7 +71,7 @@
 							{{$userName}}
 						{{end}}
 					</span>
-					<span class="time gt-df gt-ac">{{$commit.Date}}</span>
+					<span class="time gt-df gt-ac">{{DateTime "full" $commit.Date}}</span>
 				{{end}}
 			</li>
 		{{end}}