Fix psql's --help=commands output line count.

Evidently somebody neglected to update this sometime in the v10 cycle.

Patching REL_10_STABLE only; this value is about to be obsolete in
HEAD anyway.  Noted while examining \gdesc patch.

Author: tglsfdc

src/bin/psql/help.c

@@ -167,7 +167,7 @@ slashUsage(unsigned short int pager)
 	 * Use "psql --help=commands | wc" to count correctly.  It's okay to count
 	 * the USE_READLINE line even in builds without that.
 	 */
-	output = PageOutput(122, pager ? &(pset.popt.topt) : NULL);
+	output = PageOutput(124, pager ? &(pset.popt.topt) : NULL);
 
 	fprintf(output, _("General\n"));
 	fprintf(output, _("  \\copyright             show PostgreSQL usage and distribution terms\n"));