Add expected http error to code search test plan

Author: norascheuch

docs/test-plan.md

@@ -490,7 +490,7 @@ This requires running a MRVA query and seeing the results view.
 1. Make changes via config file (ensure JSON schema is helping out)
 1. Close and re-open VS Code (ensure lists are there)
 1. Collapse/expand tree nodes
-1. Create a new list, right click and select "Add repositories with GitHub Code Search". Enter the language 'python' and the query "UserMixin". This should show a rate limiting notification after a while but eventually populate the list with roughly 770 items.
+1. Create a new list, right click and select "Add repositories with GitHub Code Search". Enter the language 'python' and the query "UserMixin". This might result in an HttpError when run for the first time. If so, try again. Whene run for the second time it might show a rate limiting notification after a while or directly populate the list with roughly 900 repositories.
 
 Error cases that trigger an error notification: