biology/hyphy: Fix build with clang 13.0.0

clang 13 complains about duplicate loop unrolling pragmas for clang and
CGG. According to [1], clang supports #pragma GCC unroll with identical
semantics to #pragma clang loop unroll, so remove instances of #pragma
clang loop unroll and #pragma unroll when they appear with #pragma GCC
unroll for the same loop.

[1]
https://clang.llvm.org/docs/AttributeReference.html#pragma-unroll-pragma-nounroll

Sponsored by: The FreeBSD Foundation