bpo-33252: Document that ResourceWarning is ignored by default (GH-30358) (GH-30395)

bpo-33252: Document that ResourceWarning is ignored by default (GH-30358) (GH-30395)

`ResourceWarning` is ignored by default.

Document this behaviour, for consistency with others in this table such as `DeprecationWarning`.

Documentation PR can skip NEWS file.

Automerge-Triggered-By: GH:iritkatriel
(cherry picked from commit b949845b36b999185ed2bdf8a04dca1da39f3002)

Co-authored-by: Hugo van Kemenade <hugovk@users.noreply.github.com>
Co-authored-by: Hugo van Kemenade <hugovk@users.noreply.github.com>