WebGLState: Fix setting of NeverDepth.

[mrxz]

Description

While trying different options of depthFunc I noticed that setting it to NeverDepth didn't yield the expected result. Instead of it always failing depth testing and not rendering anything, it rendered "as normal". Looking into the code reveals that there's an if statement, presumably checking if the passed depthFunc value is "valid". However, the NeverDepth constant has the value 0 and thus fails this check. As such NeverDepth ends up being the same as the default LessEqualDepth.

This PR simply removes that if statement and associated else clause, as the else clauses matches the default case in the switch statement. This allows NeverDepth to be properly set and, unless I'm missing something obvious, behaves the same otherwise.

(Note: the diff makes it look like a lot has changed, but only the if statement and corresponding else clause have been removed, and the indentation level of the switch reduced by one)

This contribution is funded by Fern Solutions

[gkjohnson]

For an extra easy diff turn off whitespace changes:

https://github.com/mrdoob/three.js/pull/24628/files?w=1

[mrdoob]

Thanks!