fix(ci): use GITHUB_OUTPUT instead of deprecated set-output (#358)

Author: behnazh

.github/workflows/build.yaml

@@ -113,7 +113,7 @@ jobs:
         BUILD_EPOCH_PATH=$(find dist/ -type f -name "*-build-epoch.txt")
         DIGEST=$(sha256sum $TARBALL_PATH $WHEEL_PATH $REQUIREMENTS_PATH $SBOM_PATH $HTML_DOCS_PATH $BUILD_EPOCH_PATH | base64 -w0)
         echo "Digest of artifacts is $DIGEST."
-        echo "::set-output name=artifacts-sha256::$DIGEST"
+        echo "artifacts-sha256=$DIGEST" >> "$GITHUB_OUTPUT"
 
     # For now only generate artifacts for the specified OS and Python version in env variables.
     # Currently reusable workflows do not support setting strategy property from the caller workflow.