Parallel profiledbootstrap is now supported

Parallel profiledbootstrap is supported on all maintained releases. So
just remove a misleading outdated sentence, that states the opposite,
from doc/install.texi.

2014-04-26  Markus Trippelsdorf  <markus@trippelsdorf.de>

	* doc/install.texi (Building with profile feedback): Remove
	outdated sentence.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@209826 138bc75d-0d04-0410-961f-82ee72b054a4