Set INTERNAL tasking for Windows 11 ARM CI

[stefanatwork]

The Windows 11 on Arm CI job was building Embree without explicitly selecting the internal tasking backend. This updates that job to pass EMBREE_TASKING_SYSTEM=INTERNAL in the superbuild configuration.

• What changed

  • Added -DEMBREE_TASKING_SYSTEM=INTERNAL to the windows-11-arm job in .github/workflows/public.continuous.yml
  • Scoped the change to the Windows 11 ARM public CI path only

• Why this matters

  • Makes the Windows 11 ARM CI configuration align with the intended tasking backend
  • Avoids relying on the default tasking selection for this environment

• Configuration snippet

  $opts += " -DEMBREE_TESTING_INTENSITY=2"
  $opts += " -DEMBREE_TASKING_SYSTEM=INTERNAL"
  $opts += " -DCMAKE_BUILD_TYPE=Release"