R1:5d8ee504d645

Replace weird, redundant list of branches in Diffusion "Manage" UI with a link to the main branch list

Summary:
Fixes T13312. Currently, {nav Manage > Branches} has a list of branches on the same page. This has a few minor issues:

- Pager is at the top (see T13312), which is weird.
- "Default" icon is mystery meat.
- Table is kind of pointless/redundant in general?

Previously, this table had more information about technical status of each branch (autoclose/track/publish) but most of these details…