Rename behaviour to behavior in bug issue template for consistency

.gitlab/issue_templates/Bug.md

@@ -10,7 +10,7 @@
 
 (What you should see instead)
 
-### Actual behaviour
+### Actual behavior
 
 (What actually happens)
 

CHANGELOG

@@ -15,6 +15,7 @@ v 8.12.0 (unreleased)
   - Set path for all JavaScript cookies to honor GitLab's subdirectory setting !5627 (Mike Greiling)
   - Fix bug where pagination is still displayed despite all todos marked as done (ClemMakesApps)
   - Center build stage columns in pipeline overview (ClemMakesApps)
+  - Rename behaviour to behavior in bug issue template for consistency (ClemMakesApps)
   - Shorten task status phrase (ClemMakesApps)
   - Add hover color to emoji icon (ClemMakesApps)
   - Fix branches page dropdown sort alignment (ClemMakesApps)