Extension shows a subset of repos owned by a user

To reproduce: Open the extension and set `github user = StatCan`. ~25 repos are shown, but there's more like double that owned by the user. If we set `github user = StatCan/jupyter-notebooks`, we see the contents of that repo even thought it wasn't shown in the first list.

Reproduce the issue in the JupyterLab GitHub extension using the `StatCan` user and compare its repository list with the repositories visible through `StatCan/jupyter-notebooks`. Start at the extension entry point that handles the GitHub user setting and repository listing; done means all repositories owned by the user appear in the first list, including `jupyter-notebooks`.

Written by the indexing model from the issue text.