Replace explicit docker run with shell command.

* This is an attempt to fix an issue caused by GitHub composite actions attempting to pull actions before executing the docker/login-action step.

action.yaml

@@ -93,10 +93,19 @@ runs:
 
     - name: Generate SVG Diagrams
       id: generate-svg-diagrams
+      shell: bash
       if: success() && steps.changed-plantuml-files.outputs.modified_files != ''
-      uses: docker://ghcr.io/uclahs-cds/plantuml-github-action:v2.0.0
-      with:
-        args: -DPLANTUML_LIMIT_SIZE=8192 -v -tsvg ${{ steps.changed-plantuml-files.outputs.modified_files }}
+      # Using the docker image directly causes GitHub to try
+      # to pull the image before docker/login-action runs.
+      # Because this is a private image, the step would fails when this happens.
+      run: |
+        echo Generate SVG diagrams
+        docker run \
+        -v ${{ github.workspace }}:/data \
+        ghcr.io/uclahs-cds/plantuml-github-action:v2.0.0 \
+        -DPLANTUML_LIMIT_SIZE=8192 \
+        -v \
+        -tsvg ${{ steps.changed-plantuml-files.outputs.modified_files }}
 
     - name: Push Local Changes
       id: push-changes