fix: return error on reusable workflows (#1093)

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

pkg/runner/testdata/uses-workflow/push.yml

@@ -0,0 +1,9 @@
+on: push
+
+jobs:
+  reusable-workflow:
+    uses: nektos/act-tests/.github/workflows/reusable-workflow.yml@master
+    with:
+      username: mona
+    secrets:
+      envPATH: ${{ secrets.envPAT }}