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/issue/fields/textarea.tmpl

@@ -7,7 +7,6 @@
 
 	{{if $useMarkdownEditor}}
 		{{template "shared/combomarkdowneditor" (dict
-			"locale" .root.locale
 			"ContainerClasses" "gt-hidden"
 			"MarkdownPreviewUrl" (print .root.RepoLink "/markup")
 			"MarkdownPreviewContext" .root.RepoLink