Fix echo line

Author: hsubox76

.github/workflows/check-changeset.yml

@@ -16,10 +16,8 @@ jobs:
       uses: actions/setup-node@v1
       with:
         node-version: 10.x
-    - name: Yarn install
-      run: yarn
     - name: Run changeset script
       run: node scripts/check_changeset.js
       id: check-changeset
     - name: Read output
-      run: echo env.MISSING_PACKAGES
+      run: echo $MISSING_PACKAGES