fix awkward verb conjugation in cherry-pick and revert errors

app/services/commits/change_service.rb

@@ -35,7 +35,7 @@ module Commits
         success
       else
         error_msg = "Sorry, we cannot #{action.to_s.dasherize} this #{@commit.change_type_title(current_user)} automatically.
-                     It may have already been #{action.to_s.dasherize}, or a more recent commit may have updated some of its content."
+                     A #{action.to_s.dasherize} may have already been performed with this #{@commit.change_type_title(current_user)}, or a more recent commit may have updated some of its content."
         raise ChangeError, error_msg
       end
     end