This is basically a revert of 0035ba0bd1.
I couldn't confirm that allowing tearing improved FPS. Rather, this
has a potential risk to cause an error at Present of the swap chain due
to an inconsistent argument, though I have not confirmed an actual issue.
Now the DirectX 11 driver was introduced, the situation has changed.
Updates #2034
Updates #2188
CreateDXGIFactory2 is available in Windows 8.1 and newer. This is not
necessary for the current Ebitengine implementation. Use the old version
CreateDXGIFactory to support Windows 8 and older.
Updates #2613
