Update landing_session.js

Author: aduh95

lib/landing_session.js

@@ -84,11 +84,11 @@ export default class LandingSession extends Session {
   }
 
   async downloadAndPatch() {
-    const { cli, repo, owner, prid, expectedCommitShas } = this;
+    const { cli, upstream, prid, expectedCommitShas } = this;
 
     cli.startSpinner(`Downloading patch for ${prid}`);
     await runAsync('git', [
-      'fetch', `https://github.com/${owner}/${repo}.git`,
+      'fetch', upstream,
       `refs/pull/${prid}/merge`]);
     // We fetched the commit that would result if we used `git merge`.
     // ^1 and ^2 refer to the PR base and the PR head, respectively.