Revert "dix: Work around non-premultiplied ARGB cursor data harder"

This reverts commit b45c74f0.

It broke the cursor in other games. Apparently those use cursor data
with premultiplied alpha, but with some pixels having r/g/b values
larger than the alpha value (which corresponds to original r/g/b
values > 1.0), triggering the workaround.

Seems the cure turned out worse than the disease, so revert.

Bugzilla: https://bugs.freedesktop.org/108650
1 job for revert-dix-cursor-work-around-non-premultiplied-harder in 1 minute and 32 seconds (queued for 1 second)
Status Job ID Name Coverage
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passed #40626
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00:01:32