Remove useless assignment

app/services/commits/change_service.rb

@@ -37,7 +37,7 @@ module Commits
         start_branch_name: @start_branch)
 
       success
-    rescue Repository::CreateTreeError => e
+    rescue Repository::CreateTreeError
       error_msg = "Sorry, we cannot #{action.to_s.dasherize} this #{@commit.change_type_title(current_user)} automatically.
                      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