PR ld/26288: Revert obsolete part of PR ld/26047 fix

Revert commit a3fc9418 ("Stop the linker from accepting executable
ELF files as inputs to other links."), which has been made obsolete by
commit a87e1817 ("Have the linker fail if any attempt to link in an
executable is made.").  An earlier check triggers added with the latter
commit making the piece of code removed dead.

	ld/
	PR ld/26288

	Revert:
	PR 26047
	* ldelf.c (ldelf_after_open): Fail if attempting to link one
	executable into another.