vfork.2: grfix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man2/vfork.2

@@ -114,7 +114,7 @@ often needlessly, since usually immediately afterwards an
 is done.
 Thus, for greater efficiency, BSD introduced the
 .BR vfork ()
-system call, that did not fully copy the address space of
+system call, which did not fully copy the address space of
 the parent process, but borrowed the parent's memory and thread
 of control until a call to
 .BR execve (2)