2025-12-01

Some updates to the `buck2` load docs

Summary:
Some minor changes and tweaks.

I still do not like the section on loading custom rules - it seems superfluous and does not add value..but also I cannot see good reason to delete it.

Reviewed By: Wilfred

Differential Revision: D88073891

fbshipit-source-id: 8529245d285cd333aa3b6de77a1edb4c0e0ac284