Fixed typo in css class

Changed .visable-sm to .visible-sm

Fixes #23745
Signed-off-by: Rémy Coutable <remy@rymai.me>

CHANGELOG.md

@@ -13,6 +13,7 @@ Please view this file on the master branch, on stable branches it's out of date.
   - Fixed link typo on /help/ui to Alerts section. !6915 (Sam Rose)
   - Fix filtering of milestones with quotes in title (airatshigapov)
   - Simpler arguments passed to named_route on toggle_award_url helper method
+  - Fix typo in framework css class. !7086 (Daniel Voogsgerd)
   - Fix: Backup restore doesn't clear cache
   - API: Fix project deploy keys 400 and 500 errors when adding an existing key. !6784 (Joshua Welsh)
   - Replace jquery.cookie plugin with js.cookie !7085

app/assets/stylesheets/framework/header.scss

@@ -227,7 +227,7 @@ header {
       float: none !important;
 
       .visible-xs,
-      .visable-sm {
+      .visible-sm {
         display: table-cell !important;
       }
     }