Remove a duplicate store when performing REL32 relocations in rtld.

The duplicate call to store_ptr() was added in r204687, but it should
have no effect as it only stores an Elf_Sword and the later store_ptr()
does a write that is at least as large if not larger.

Reviewed by: jmallett
Obtained from: CheriBSD (sort of)
Sponsored by: DARPA / AFRL