Use https://gitbox.apache.org/repositories.json rather than scanning GitHub

Prefer using Infra data - https://gitbox.apache.org/repositories.json - to scanning GitHub.

This simplifies the code - no need for a GH token.
The GH list also contains at least one misleading repo:
https://github.com/apache/comdev-reporter
This means that its commit activity is not shown.

Start by locating the code that scans GitHub repositories and identify how it obtains and uses the repository list. Read the Infra data at https://gitbox.apache.org/repositories.json and trace the current commit-activity path. Done means the implementation uses that source, no longer requires a GitHub token for this lookup, and does not treat apache/comdev-reporter as a repository whose activity is shown.

Written by the indexing model from the issue text.