ci improvements - fixing buildx with cache

Author: tsviz

.github/workflows/ci.yml

@@ -228,7 +228,7 @@ jobs:
           context: . # using the current directory as the context
           push: true # push the docker image to the registry
           tags: ghcr.io/${{ github.repository }}:${{ github.run_number }} # tag the docker image with the current run number from the github action workflow run
-          cache-from: type=registry,ref=ghcr.io/${{ github.repository }}:${{ github.run_number }} 
+          cache-from: type=registry,ref=ghcr.io/${{ github.repository }}:$((${{ github.run_number }}-1)) 
           cache-to: type=inline
 
   runner-indexes: # job to generate the runner indexes for the uat-parallel-tests job