fix(ghrunner): fix release pipeline for self-hosted runner (#994)

* Altinn has uppercase, thats not allowed in ghcr.io
* Remove ghrunner- prefix from image tag

---------

Co-authored-by: tjololo <1145298+tjololo@users.noreply.github.com>
Co-authored-by: Renato Monteiro <45536168+monteiro-renato@users.noreply.github.com>

.github/workflows/gh-runner-release.yml

@@ -14,11 +14,12 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - name: Get version from tags
-        id: version
+      - name: Get variables from tags
+        id: vars
         run: |
-          tag=${GITHUB_REF/refs\/tags\//}
+          tag=${GITHUB_REF/refs\/tags\/ghrunner-/}
           echo "version=${tag%-demo}" >> $GITHUB_OUTPUT
+          echo "reponame=${GITHUB_REPOSITORY,,}" >>${GITHUB_OUTPUT}
       - name: Get Git commit timestamps
         run: echo "TIMESTAMP=$(git log -1 --pretty=%ct)" >> $GITHUB_ENV
       - name: Set up QEMU
@@ -38,6 +39,6 @@ jobs:
           context: ./infrastructure/images/gh-runner
           push: true
           platforms: linux/amd64,linux/arm64
-          tags: ghcr.io/${{ github.repository }}/gh-runner:v${{ steps.version.outputs.version }}
+          tags: ghcr.io/${{ steps.vars.outputs.reponame }}/gh-runner:v${{ steps.vars.outputs.version }}
         env:
-          SOURCE_DATE_EPOCH: ${{ env.TIMESTAMP }}
+          SOURCE_DATE_EPOCH: ${{ env.TIMESTAMP }}