Remove stale boot message for fstrim.

Following commit a1131b1763efa56fe4fcaddf712a984a7d2d47da, where a
dexopt progress dialogue that applied to upgrades from pre-N versions
was removed.

Test: Boot
Bug: 251903639
Change-Id: Id436a861b8cb353ca0c10fa0b54c058ec6b69cab
1 file changed