Revert "docker-image-build.yml: Don't trigger on docker-image-common.yml."

This reverts commit 2bf2cee.

Author: samsrabin

.github/workflows/docker-image-build.yml

@@ -9,12 +9,14 @@ on:
     paths:
       - 'doc/ctsm-docs_container/**'
       - '!doc/ctsm-docs_container/README.md'
+      - '.github/workflows/docker-image-common.yml'
 
   pull_request:
     # Run on pull requests that change the listed files
     paths:
       - 'doc/ctsm-docs_container/**'
       - '!doc/ctsm-docs_container/README.md'
+      - '.github/workflows/docker-image-common.yml'
 
   workflow_dispatch: