Fix button text wrapping to next line

Bootstrap removed white-space nowrap from buttons in v4.2.1,
causing at least one bug, so this commit re-adds that style
to all buttons

app/assets/stylesheets/framework/buttons.scss

@@ -139,6 +139,7 @@
   @include btn-white;
 
   color: $gl-text-color;
+  white-space: nowrap;
 
   &:focus:active {
     outline: 0;

changelogs/unreleased/60116-fix-button-wrapping.yml

+---
+title: Add to white-space nowrap to all buttons
+merge_request: 27069
+author:
+type: fixed