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/repo/wiki/new.tmpl

@@ -23,7 +23,6 @@
 				{{$content = .locale.Tr "repo.wiki.welcome"}}
 			{{end}}
 			{{template "shared/combomarkdowneditor" (dict
-				"locale" $.locale
 				"MarkdownPreviewUrl" (print .Repository.Link "/markup")
 				"MarkdownPreviewContext" .RepoLink
 				"TextareaName" "content"