Remove obsolete CSS text classes (#30576)

- `.text-thin` and `.text-italic` are not present in CSS so were doing nothing and I removed them.
- `.text.middle` was unused so I removed it.
- `.text.italic` is replaced with `tw-italic`.
- `.text.normal` had exactly one use and it wasn't even needed.
- add a `muted` class to the link to `org_profile_avatar.tmpl`.

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Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

templates/repo/settings/options.tmpl

@@ -135,7 +135,7 @@
 									<form method="post" class="tw-inline-block">
 										{{.CsrfTokenHtml}}
 										<input type="hidden" name="action" value="mirror-sync">
-										<button class="ui primary tiny button inline text-thin">{{ctx.Locale.Tr "repo.settings.sync_mirror"}}</button>
+										<button class="ui primary tiny button inline">{{ctx.Locale.Tr "repo.settings.sync_mirror"}}</button>
 									</form>
 								</td>
 							</tr>