chore: replace deprecated set-output command (#43)

Signed-off-by: Niccolò Fei <niccolo.fei@enterprisedb.com>

.github/workflows/build.yml

@@ -44,7 +44,6 @@ jobs:
         platforms: ${{ matrix.platforms }}
 
     - name: Docker meta
-      id: docker-meta
       env:
         TAGS: ${{ toJson(matrix.tags) }}
       run: |
@@ -58,10 +57,9 @@ jobs:
             RESULT="${RESULT},ghcr.io/${IMAGE_RELEASE}:${tag}"
           fi
         done
-        echo "::set-output name=tags::${RESULT%,}"
+        echo "TAGS=${RESULT%,}" >> $GITHUB_ENV
 
     - name: Set up Docker Buildx
-      id: buildx
       uses: docker/setup-buildx-action@v2
 
     - name: Log in to the GitHub Container registry
@@ -78,7 +76,7 @@ jobs:
         file: ${{ matrix.file }}
         push: false
         load: true
-        tags: ${{ steps.docker-meta.outputs.tags }}
+        tags: ${{ env.TAGS }}
 
     - name: Dockle scan
       uses: erzz/dockle-action@v1
@@ -96,4 +94,4 @@ jobs:
         file: ${{ matrix.file }}
         platforms: ${{ matrix.platforms }}
         push: true
-        tags: ${{ steps.docker-meta.outputs.tags }}
+        tags: ${{ env.TAGS }}