Fix texture-component-swizzle typo

[greggman]

Chromium CQ test here

[greggman]

This turned into a bigger change than just fixing the typo.
With the typo fixed, a bunch of tests started failing.
One issue in particular is that out of bounds textureLoad
needs to take swizzle into account since its allowed to
return any value inside the texture. I'm making the assuption
that the spec would say it can return any swizzled value in
the texture and filed gpuweb/gpuweb#5437
though with that assumption the test pass again.

This comes up with depth textures because if texture-component-swizzle
is enabled then we check RGBA for depth textures instead of just R
and we expcet GBA to be 001. Before this change, if the texel address
was invalid we'd get a texel from the software texture and GBA would
be wrong and so no texels would match.

Theoretically, with this change, the software sampler code supports
swizzles but, that path is not really be exercised. Only the fact that
depth textures go from R??? to R001 when 'texture-component-swizzle'
is enabled is exercised.

It seems to be passing now. The failure there seem related to #4495

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