Roll Flutter Engine from 78c63d3c2c68 to 9869d47a2736 (1 revision) (f…

…lutter#142842)

flutter/engine@78c63d3...9869d47

2024-02-02 [email protected] [Impeller] Allow playgrounds to use SwiftShader via a flag. (flutter/engine#50298)

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 [email protected],[email protected],[email protected] 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

@@ -1 +1 @@
-78c63d3c2c68b57e6343e756aa16c0ae963686e1
+9869d47a2736e75470985949137241c48457bf50