Log Message:
binutils: remove now unneeded OpenBSD specific checks in gold.

Support for DT_INIT_ARRAY, DT_FINI_ARRAY and DT_PREINIT_ARRAY was added
in 2016 [1], and support for DT_RUNPATH in 2017 [2].

[1] https://marc.info/?l=openbsd-cvs&m=147193481229072&w=2
[2] https://marc.info/?l=openbsd-cvs&m=148504804104054&w=2