CI: Replace the deprecated `::set-output` command by writing to $GITHUB_OUTPUT in workflow definition

See "CI: Replace the deprecated `::set-output` command by writing to
$GITHUB_OUTPUT in matrix.py" for the reasoning behind this commit.

(cherry picked from commit b87ecbb179b897521aa217a3341ba5529b36f447)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 0855bad3117bd027795303d717e39cebc6ebadaa)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 824ed8f40926f1ee2624a5988708202367c6c126)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/.github/workflows/vtest.yml b/.github/workflows/vtest.yml
index ea39662..70ea9ca 100644
--- a/.github/workflows/vtest.yml
+++ b/.github/workflows/vtest.yml
@@ -50,7 +50,7 @@
     - name: Generate cache key
       id: generate-cache-key
       run: |
-        echo "::set-output name=key::$(echo ${{ matrix.name }} | sha256sum | awk '{print $1}')"
+        echo "key=$(echo ${{ matrix.name }} | sha256sum | awk '{print $1}')" >> $GITHUB_OUTPUT
 
     - name: Cache SSL libs
       if: ${{ matrix.ssl && matrix.ssl != 'stock' && matrix.ssl != 'BORINGSSL=yes' && matrix.ssl != 'QUICTLS=yes' }}
@@ -138,7 +138,7 @@
         fi
         echo "::endgroup::"
         haproxy -vv
-        echo "::set-output name=version::$(haproxy -v |awk 'NR==1{print $3}')"
+        echo "version=$(haproxy -v |awk 'NR==1{print $3}')" >> $GITHUB_OUTPUT
     - name: Install problem matcher for VTest
       # This allows one to more easily see which tests fail.
       run: echo "::add-matcher::.github/vtest.json"