feat: disable buildx step by default

The `setup-buildx` step within the workflow has been known to cause
issue when pushing images to Pulp registry < `3.32.0`.

There was a concern surrounding the lack of buildx step potentially
leading to a situation where the kayobe-config remains inside the image.
However, this does not appear to be the case.

Author: jackhodgkiss

roles/github/defaults/main.yml

@@ -23,7 +23,7 @@ github_kayobe_hook: ""
 
 github_final_hook: ""
 
-github_buildx_enabled: true
+github_buildx_enabled: false
 
 github_buildx_inline_config: ""