Syntax warnings from improperly formatted comparisons

[ThatAsherGuy]

They recently bumped the python version for the Blender dailies, which means that using identity checks on literals — using is and is not instead of == and != when you're doing comparisons with numbers and strings — will now produce syntax warnings.

It looks like there's only a handful to fix, but I figured it'd be helpful to know in advance, so you don't have to deal with a bunch of duplicate reports when 2.93 ships.

[Radivarig]

Thanks!