Fix dashboard UI bugs and more (#14767)

This PR fixes a few UI bugs I spontaneously encountered:

- Fixes emojis in repo titles getting head-cut and tail-cut in dashboard feed due to introduction of 1.25 em emojis at 1 em line-height, by simply using the original 1 3/7 em value of `semantic.css`
- Fixes regression (too long repo names should be capped to 70%) in #13828 due to flex children not respecting properties like `overflow: hidden;`, and removes a block of dead style code
- Follow-up to #14761, removes extraneous code for top navbar and correct right margin for Font Awesome
- Fixes color emphasis inversion in arc-green theme for top right buttons (edit, delete) on commit view boxes

templates/base/head_navbar.tmpl

@@ -173,7 +173,7 @@
 						<div class="divider"></div>
 
 						<a class="{{if .PageIsAdmin}}active{{end}} item" href="{{AppSubUrl}}/admin">
-							<i class="icon settings"></i>
+							{{svg "octicon-server"}}
 							{{.i18n.Tr "admin_panel"}}<!-- Admin Panel -->
 						</a>
 					{{end}}