Darwin: Address a translation comment [PR104552].

This amends an error message to correct punctuation and a little
better wording.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>

	PR translation/104552

gcc/ChangeLog:

	* config/host-darwin.cc (darwin_gt_pch_get_address): Amend
	the PCH out of memory error message punctuation and wording.