ci: set TEST_ARGS manually (leanprover#422)

Pending leanprover/lean-action#153, manually set
`TEST_ARGS`. As can be seen from the CI runs, this now correctly results
in running `lake test --wfail --iofail`.

Author: chenson2018

.github/workflows/lean_action_ci.yml

@@ -14,6 +14,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+      - name: Set TEST_ARGS manually
+        run: |
+          echo "TEST_ARGS='--wfail --iofail'" >> $GITHUB_ENV
+        shell: bash
       - uses: leanprover/lean-action@v1
         with:
           build-args: "--wfail --iofail"