Remove stale boot message for fstrim.

Following commit a1131b1763, where a
dexopt progress dialogue that applied to upgrades from pre-N versions
was removed.

Test: Boot
Bug: 251903639
Change-Id: Id436a861b8cb353ca0c10fa0b54c058ec6b69cab

services/core/java/com/android/server/pm/PackageManagerService.java

@@ -2950,15 +2950,6 @@ public class PackageManagerService implements PackageSender, TestUtilityService
                     }
                 }
                 if (doTrim) {
-                    if (!isFirstBoot()) {
-                        try {
-                            ActivityManager.getService().showBootMessage(
-                                    mContext.getResources().getString(
-                                            R.string.android_upgrading_fstrim),
-                                    true);
-                        } catch (RemoteException e) {
-                        }
-                    }
                     sm.runMaintenance();
                 }
             } else {