fix workflow substitution

fix var -> vars

.github/workflows/update-homelab.yml

@@ -30,7 +30,7 @@ jobs:
       - name: replace domain in configs
         run: |
           # add any other files that need domain substituion here - for flexablity
-          sed -i -e 's/$DOMAIN/{{ var.DOMAIN }}/g' ./dashy/conf.yml
+          sed -i -e 's/$DOMAIN/${{ vars.DOMAIN }}/g' ./dashy/conf.yml
 
       - name: install docker compose for tests
         uses: KengoTODA/actions-setup-docker-compose@v1