Add missing newline to correct failure of the regression test.

According to IEEE Std 1003.1, 2004 "Whenever the pattern space is
written to standard output or a named file, sed shall immediately
follow it with a <newline>."

An attempt at the same correction might have been made with r1.3,
which is however identical with r1.2.

tools/regression/usr.bin/sed/regress.y.out

@@ -1 +1 @@
-fOO
+fOO