Remove black labels and CSS cleanup (#21003)

Co-authored-by: John Olheiser <john.olheiser@gmail.com>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

Author: 3 people

Diff for: templates/org/menu.tmpl

@@ -18,7 +18,7 @@
 			<a class="{{if $.PageIsOrgTeams}}active{{end}} item" href="{{$.OrgLink}}/teams">
 				{{svg "octicon-people"}}&nbsp;{{$.locale.Tr "org.teams"}}
 				{{if .NumTeams}}
-					<div class="ui black label">{{.NumTeams}}</div>
+					<div class="ui primary label">{{.NumTeams}}</div>
 				{{end}}
 			</a>
 		{{end}}

Diff for: templates/user/overview/header.tmpl

@@ -39,7 +39,7 @@
 					<a class="item" href="{{$.OrgLink}}/teams">
 						{{svg "octicon-people"}}&nbsp;{{$.locale.Tr "org.teams"}}
 						{{if .NumTeams}}
-							<div class="ui black label">{{.NumTeams}}</div>
+							<div class="ui primary label">{{.NumTeams}}</div>
 						{{end}}
 					</a>
 				{{end}}

Diff for: web_src/less/themes/theme-arc-green.less

@@ -339,10 +339,6 @@ td.blob-hunk {
   color: var(--color-secondary-dark-6);
 }
 
-.repository.labels .ui.basic.black.label {
-  background-color: #bbbbbb !important;
-}
-
 .lines-num {
   color: var(--color-secondary-dark-6) !important;
   border-color: var(--color-secondary) !important;