Use the correct action input parameter

Author: aeisenberg

.github/workflows/__with-checkout-path.yml

@@ -12,7 +12,7 @@ steps:
       tools: ${{ steps.prepare-test.outputs.tools-url }}
       # it's enough to test one compiled language and one interpreted language
       languages: csharp,javascript
-      source-path: x/y/z/some-path/tests/multi-language-repo
+      source-root: x/y/z/some-path/tests/multi-language-repo
       debug: true
   - name: Build code (non-windows)
     shell: bash