Replace set-env to fix tagging (#74)

Author: mattmook

.github/workflows/main.yml

@@ -50,7 +50,7 @@ jobs:
       run: ./gradlew --build-cache assemble check --stacktrace
 
     - name: Set tag version
-      run: echo ::set-env name=CIRCLE_TAG::$(echo ${GITHUB_REF:10})
+      run: echo "CIRCLE_TAG=$(echo ${GITHUB_REF:10})" >> $GITHUB_ENV
       if: startsWith(github.ref, 'refs/tags/')
 
     - name: Upload tag