build: Ensure all required checks run on merge_group

And clean up some of the whitespace formatting so that the "name" and
"on" are grouped away from the "jobs".

Signed-off-by: Rob Bradford <rbradford@rivosinc.com>

.github/workflows/docker-image.yaml

@@ -1,5 +1,4 @@
 name: Cloud Hypervisor's Docker image update
-
 on:
   push:
     branches: main