Provide description for LOCAL_MULTI_THREADING runtime mode in OSS version.
Provide description for LOCAL_MULTI_THREADING runtime mode in OSS version.

PiperOrigin-RevId: 407526804
Change-Id: I55a74139669388f865372ab22d946322a25cc200

deepmind/launchpad,deepmind/launchpad,deepmind/launchpad,deepmind/launchpad