gas: drop old cygnus install hack

This was needed when gas was using the automake cygnus option, but
this was removed years ago by Simon in d0ac1c44885daf68f631befa37e
("Bump to autoconf 2.69 and automake 1.15.1").  So delete it here.
The info pages are already & still installed by default w/out it.
2 files changed