prevent project dropdown chevron from disappearing in small viewports

CHANGELOG

@@ -31,6 +31,7 @@ v 8.12.0 (unreleased)
   - Add horizontal scrolling to all sub-navs on mobile viewports (ClemMakesApps)
   - Fix markdown help references (ClemMakesApps)
   - Add last commit time to repo view (ClemMakesApps)
+  - Fix accessibility and visibility of project list dropdown button !6140
   - Added project specific enable/disable setting for LFS !5997
   - Don't expose a user's token in the `/api/v3/user` API (!6047)
   - Remove redundant js-timeago-pending from user activity log (ClemMakesApps)

app/assets/stylesheets/framework/header.scss

@@ -136,6 +136,8 @@ header {
     }
 
     .title {
+      position: relative;
+      padding-right: 20px;
       margin: 0;
       font-size: 19px;
       max-width: 400px;
@@ -163,11 +165,11 @@ header {
         color: $gl-text-color;
         border: transparent;
         background: transparent;
-        position: relative;
-        top: -2px;
+        position: absolute;
+        right: 3px;
         width: 12px;
-        line-height: 12px;
-        margin-left: 5px;
+        line-height: 19px;
+        margin-top: (($header-height - 19) / 2);
         padding: 0;
         font-size: 10px;
         text-align: center;