Remove unneeded color argument in Clear() method following changes in PR #161

[txoof]

Aligns the example/demo code in PR #161

[SSYYL]

Why not modify Clear(self) to support a specified color?

[txoof]

The 2in7 display does not support color and the Clear() method doesn't appear to even use the "color" argument. It just sends 0xFF and that appears to work.

I'm not sure why the color arg is even here. Removing it would align the 2in7 with the Clear() method in both the 2in7b and V2. See line 246.

If it makes more sense to have a color arg, perhaps it would be a good idea to update the 2in7b/V2 to match. Either way, it would make it more consistent to have the same methods wherever possible.

I can produce a PR for either at your preference.

[SSYYL]

I think providing color options is a good way to do it. Black or white is also a choice(Black is probably used less often).

[txoof]

Ok, I'll close this PR and submit an alternative with the color option.