[net processing] Change MaybeSendAddr() to take a reference

Summary:
Change name of CNode parameter to node now that it's no longer a pointer.

This is a backport of core#21236 [4/6]
https://github.com/bitcoin/bitcoin/pull/21236/commits/c87423c58b5165de835a49bebd566538a70c07ab

Depends on D10917

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D10918