TEST_MAPPING: enable Ravenwood in postsubmit

Ravenwood is already running in presubmit elsewhere.
Enabling it in postsubmit here on omakoto@'s advice.

Bug: 292141694
Test: visual confirmation of `git diff`
Change-Id: I4d4aae5497a1cb31a6a9b098518aae6d9a9c2702
Signed-off-by: Lucas Henneman <henneman@google.com>