Roll Flutter Engine from 670e85f184d3 to 9a3494e31171 (2 revisions) (#138191)

https://github.com/flutter/engine/compare/670e85f184d3...9a3494e31171

2023-11-09 jonahwilliams@google.com [Impeller] Remove unused/untested Path APIs. (flutter/engine#47841)
2023-11-09 athom@google.com Remove references to the runtime/third_party directory in the Dart SDK (flutter/engine#47853)

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 bdero@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

-670e85f184d3da10da7e0abcbc3b4a23496d3bfa
+9a3494e31171573cee7a186c0ce419861e10b6cc