Fix syntax and varaible subs in workflow file.

The previous version did not include the "actions" prefix on the
checkout task. Substitution and filtering of the version variable was
also improved to match that of the release workflow.

Eventually we will want to reuse more job artifacts instead of running
builds and documentation multiple times.

.github/workflows/publish.yaml

@@ -1,5 +1,4 @@
----
-name: Deploy collection to galaxy
+name: publish
 on:
   release:
     types:
@@ -10,18 +9,18 @@ jobs:
     name: Publish to Galaxy
     runs-on: ubuntu-latest
     steps:
-      - uses: checkout@v4
+      - uses: actions/checkout@v4
         with:
           ref: ${{ github.ref }}
 
       - name: Build collection
         run: ansible-galaxy collection build
 
       - name: Get expected version string
-        shell: VERSION=$(echo ${{ github.ref_name }} | sed -e 's/v\(.*\)/\1/'
+        shell: echo "VERSION={$GITHUB_REF_NAME:1}" >> "$GITHUB_ENV"
 
       - name: Publish to Galaxy
         run: |
           ansible-galaxy collection publish \
-          tofugarden-secureboot-$VERSION.tar.gz \
+          tofugarden-secureboot-${{ env.VERSION }}.tar.gz \
           --token ${{ secrets.GALAXY_API_KEY }}