Revert "ci: pin buildx latest to v0.18.0"

This reverts commit 4ea16daf18.

Buildx v0.19.1 has been released.

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

.github/workflows/buildx-releases-json.yml

@@ -22,7 +22,6 @@ jobs:
       repository: docker/buildx
       artifact_name: buildx-releases-json
       filename: buildx-releases.json
-      pin_latest: v0.18.0
     secrets: inherit
 
   open-pr: