CSS tweaks to warning/error segments and misc fixes (#13024)

* CSS tweaks to warning/error segments and misc fixes

- Adjust styling for warning/error in arc-green
- Change danger boxes from orange to red
- Fix code highlight text color in arc-green
- Fix warning message in arc-green
- Fix border in org member list in arc-green
- Fix disabled checkbox text in arc-green

* use same selector in gitea theme

* fix blame highlight

Co-authored-by: zeripath <art27@cantab.net>

templates/org/settings/delete.tmpl

@@ -6,10 +6,10 @@
 			{{template "org/settings/navbar" .}}
 			<div class="twelve wide column content">
 				{{template "base/alert" .}}
-				<h4 class="ui top attached warning header">
+				<h4 class="ui top attached error header">
 					{{.i18n.Tr "org.settings.delete_account"}}
 				</h4>
-				<div class="ui attached warning segment">
+				<div class="ui attached error segment">
 					<div class="ui red message">
 						<p class="text left">{{svg "octicon-alert"}} {{.i18n.Tr "org.settings.delete_prompt" | Str2html}}</p>
 					</div>