Fix old typo in comment.

NFAs have children, but their individual states don't.

src/include/regex/regguts.h

@@ -331,8 +331,8 @@ struct nfa
 	color		bos[2];			/* colors, if any, assigned to BOS and BOL */
 	color		eos[2];			/* colors, if any, assigned to EOS and EOL */
 	size_t		size;			/* Current NFA size; differs from nstates as
-								 * it also counts the number of states created
-								 * by children of this state. */
+								 * it also counts the number of states in
+								 * children of this NFA. */
 	struct vars *v;				/* simplifies compile error reporting */
 	struct nfa *parent;			/* parent NFA, if any */
 };