Fix invalid API call when running locally

The method getAnalysisKey would call getWorkflowPath and raise an API Error.

This change follows the pattern in prepareLocalRunEnvironment to set a dummy value for the required environment variable, therefore shortcutting the API request.

Author: Simon Engledew

CONTRIBUTING.md

@@ -36,6 +36,7 @@ It is possible to run this action locally via [act](https://github.com/nektos/ac
 
   ```bash
   CODEQL_LOCAL_RUN=true
+  GITHUB_SERVER_URL=https://github.com
 
   # Optional, for better logging
   GITHUB_JOB=<ANY_JOB_NAME>