binutils: Remove unused substitution PROGRAM

binutils: Remove unused substitution PROGRAM

Unlike other substitution, this substitution of @PROGRAM@ was done in
binutils/Makefile and it was intended for binutils/cxxfilt.man.  @PROGRAM@
in binutils/cxxfilt.man is removed in the commit 0285c67df190 ("Automate
generate on man pages") in 2001 and @PROGRAM@ is ineffective since then.

Because PROGRAM substitution does nothing, removing this manual
substitution should be completely safe.

binutils/ChangeLog:

	* doc/local.mk: Remove unused substitution PROGRAM.
	* Makefile.in: Regenerate.