libstdc++: Remove __find_if unrolling for random access iterators

libstdc++: Remove __find_if unrolling for random access iterators

As the numbers in PR libstdc++/88545 show, the manual loop unrolling in
std::__find_if doesn't actually help these days, and it prevents the
compiler from auto-vectorizing.

Remove the dispatching on iterator_category and just use the simple loop
for all iterator categories.

libstdc++-v3/ChangeLog:

	* include/bits/stl_algobase.h (__find_if): Remove overloads for
	dispatching on iterator_category. Do not unroll loop manually.
	* include/bits/stl_algo.h (__find_if_not): Remove
	iterator_category argument from __find_if call.