Fix call to invalid step output in the deploy-mainnet workflow (#937)

.github/workflows/deploy-mainnet.yml

@@ -22,8 +22,8 @@ jobs:
         id: vars
         shell: bash
         run: |
-          echo "##[set-output name=branch;]$(echo ${GITHUB_REF##*/})"
-          echo "::set-output name=sha_short::$(git rev-parse --short HEAD)"
+          echo "branch=${GITHUB_REF##*/}" >> $GITHUB_OUTPUT
+          echo "sha_short=$(git rev-parse --short HEAD)" >> $GITHUB_OUTPUT
 
       - name: Configure AWS credentials
         uses: aws-actions/configure-aws-credentials@v1
@@ -84,8 +84,8 @@ jobs:
       - name: S3 CI | Download release runtime from S3 bucket
         shell: bash
         env:
-          S3BUCKET_URL: s3://${{ secrets.CI_MAINNET_S3BUCKET_NAME }}/builds/aleph-node/commits/${{ steps.get_branch.outputs.sha_short }}/aleph-runtime
-          S3BUCKET_FILE: aleph-runtime-${{ steps.get_branch.outputs.sha_short }}.tar.gz
+          S3BUCKET_URL: s3://${{ secrets.CI_MAINNET_S3BUCKET_NAME }}/builds/aleph-node/commits/${{ steps.vars.outputs.sha_short }}/aleph-runtime
+          S3BUCKET_FILE: aleph-runtime-${{ steps.vars.outputs.sha_short }}.tar.gz
         run: |
           aws s3 cp ${{ env.S3BUCKET_URL }}/${{ S3BUCKET_FILE }} ${{ env.S3BUCKET_FILE }}
 
@@ -94,7 +94,7 @@ jobs:
         if: startsWith(github.ref, 'refs/tags/')
         with:
           files: |
-            aleph-runtime-${{ steps.get_branch.outputs.sha_short }}.tar.gz
+            aleph-runtime-${{ steps.vars.outputs.sha_short }}.tar.gz
 
       - name: GIT | Checkout aleph-apps repo
         uses: actions/checkout@master