Move rescue clause to branch creation method

In https://gitlab.com/gitlab-org/gitlab/-/merge_requests/37082
we consolidated the `trigger-build-docs` script into the
`trigger-build` one. A new `cancel_latest_pipeline!` method was
created, but the rescue clause of the branch creation was misplaced.
It should actually be a part of `create_remote_branch!` instead.

scripts/trigger-build

@@ -274,6 +274,8 @@ module Trigger
     def create_remote_branch!
       Gitlab.create_branch(downstream_project_path, ref, 'master')
       puts "=> Remote branch '#{ref}' created"
+    rescue Gitlab::Error::BadRequest
+      puts "=> Remote branch '#{ref}' already exists!"
     end
 
     def cancel_latest_pipeline!
@@ -292,8 +294,6 @@ module Trigger
 
       # Cancel the pipeline
       Gitlab.cancel_pipeline(downstream_project_path, pipeline_id)
-    rescue Gitlab::Error::BadRequest
-      puts "=> Remote branch '#{ref}' already exists!"
     end
 
     def display_success_message