getpriority.2: ffix

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

man2/getpriority.2

@@ -124,6 +124,7 @@ returns the calling thread's nice value, which may be a negative number.
 On error, it returns \-1 and sets
 .I errno
 to indicate the cause of the error.
+.PP
 Since a successful call to
 .BR getpriority ()
 can legitimately return the value \-1, it is necessary