Annotate partial rerelease branches as likely to be "retain".
Annotate partial rerelease branches as likely to be "retain".

The vast majority of usage is for the default of "retain" rather than the
opt-out of "return".

PiperOrigin-RevId: 482822912
Change-Id: Ibc4be4eac5d8f240a540f67c890551da67464a54

google/tcmalloc,google/tcmalloc,google/tcmalloc