fix: heuristicInstanceUrl is async, so await it

src/git_service.js

@@ -91,7 +91,7 @@ const fetchCurrentInstanceUrl = async workspaceFolder => {
   }
 
   // try to determine the instance URL heuristically
-  const heuristicUrl = heuristicInstanceUrl(workspaceFolder);
+  const heuristicUrl = await heuristicInstanceUrl(workspaceFolder);
   if (heuristicUrl) {
     return heuristicUrl;
   }