www/firefox: drop obsolete patch

In Skia m125 all extra ARM feature detection was removed
(ref skia 571b4cf2e359), so we do not have to roll our own.
This also should fix built on ARM, which was failing over
the detection of native CRC32 instructions (which are not used
anymore by Skia, and whose dis-use triggered the whole feature
detection removal)

Reported by: eduardo@