cleanup locale function usage (#27227) (#27240)

Backport #27227 by @denyskon

Throughout the Gitea codebase, you can meet some weird constructions to
make `locale.Tr` work in subtemplates.
Since we now have `ctx.Locale.Tr` which solves that problem, clean up
various templates which pass `locale` through `dict` or use some weird
constructions like `$.root.locale`

Going on, it would be great to replace every case of `$.locale.Tr` and
`.locale.Tr` with `ctx.Locale.Tr`, but that needs to be done with
patience.

Co-authored-by: Denys Konovalov <kontakt@denyskon.de>

templates/projects/list.tmpl

@@ -23,7 +23,7 @@
 	<form class="list-header-search ui form ignore-dirty">
 		<div class="ui small search fluid action input">
 			<input type="hidden" name="state" value="{{$.State}}">
-			{{template "shared/searchinput" dict "locale" .locale "Value" .Keyword}}
+			{{template "shared/searchinput" dict "Value" .Keyword}}
 			<button class="ui small icon button" type="submit" aria-label="{{.locale.Tr "explore.search"}}">
 				{{svg "octicon-search"}}
 			</button>