[Windows] remove unused extra frame rate doubling for interlaced resolutions in CVideoSyncD3D

[CrystalP]

Description

The Interlaced() function always returns false anyway due to initialization of m_interlaced to false and no code to change the value. It is not an overriden virtual function and looks like a left over from old code.
For interlaced resolutions, DeviceResources::GetDisplayMode() provides frame rate doubling.

The Xbox code doesn't have frame rate doubling but the hdmi information doesn't signal interlaced resolutions. The Xbox likely doesn't support interlaced resolutions.
@thexai could you confirm?

Motivation and context

Cleanup leftovers of old code.

How has this been tested?

Don't have a screen that reports interlaced resolutions anymore. No change for progressive resolutions on Windows 10.

What is the effect on users?

None.

Types of change

• Bug fix (non-breaking change which fixes an issue)
• Clean up (non-breaking change which removes non-working, unmaintained functionality)
• Improvement (non-breaking change which improves existing functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that will cause existing functionality to change)
• Cosmetic change (non-breaking change that doesn't touch code)
• None of the above (please explain below)

Checklist:

• My code follows the Code Guidelines of this project
• My change requires a change to the documentation, either Doxygen or wiki
• I have updated the documentation accordingly
• I have read the Contributing document
• I have added tests to cover my change
• All new and existing tests passed

[thexai]

Yes, Xbox (at least current models) not supports interlaced display modes and if any old model supports it is not handled anyway in current code.