Roll Flutter Engine from 8c43332c6ffc to 39415c3eed42 (1 revision) (#142740)

https://github.com/flutter/engine/compare/8c43332c6ffc...39415c3eed42

2024-02-01 30870216+gaaclarke@users.noreply.github.com [Impeller] added an assert that goldens are generated (flutter/engine#50222)

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-engine-flutter-autoroll
Please CC matanl@google.com,rmistry@google.com,zra@google.com on the revert to ensure that a human
is aware of the problem.

To file a bug in Flutter: https://github.com/flutter/flutter/issues/new/choose

To report a problem with the AutoRoller itself, please file a bug:
https://issues.skia.org/issues/new?component=1389291&template=1850622

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

bin/internal/engine.version

-8c43332c6ffc93529d476c8f1808cfa010232a90
+39415c3eed42917047001749ce9058042d1aca0f