Fix inconsistencies in psql --help=commands

The set of subcommands supported by \dAp, \do and \dy was described
incorrectly in psql's --help.  The documentation was already consistent
with the code.

Reported-by: inoas, from IRC
Author: Matthijs van der Vleuten
Reviewed-by: Neil Chen
Discussion: https://postgr.es/m/6a984e24-2171-4039-9050-92d55e7b23fe@www.fastmail.com
Backpatch-through: 9.6

Author: michaelpq

src/bin/psql/help.c

@@ -248,7 +248,7 @@ slashUsage(unsigned short int pager)
 	fprintf(output, _("  \\dL[S+] [PATTERN]      list procedural languages\n"));
 	fprintf(output, _("  \\dm[S+] [PATTERN]      list materialized views\n"));
 	fprintf(output, _("  \\dn[S+] [PATTERN]      list schemas\n"));
-	fprintf(output, _("  \\do[S]  [PATTERN]      list operators\n"));
+	fprintf(output, _("  \\do[S+] [PATTERN]      list operators\n"));
 	fprintf(output, _("  \\dO[S+] [PATTERN]      list collations\n"));
 	fprintf(output, _("  \\dp     [PATTERN]      list table, view, and sequence access privileges\n"));
 	fprintf(output, _("  \\dP[itn+] [PATTERN]    list [only index/table] partitioned relations [n=nested]\n"));
@@ -261,7 +261,7 @@ slashUsage(unsigned short int pager)
 	fprintf(output, _("  \\du[S+] [PATTERN]      list roles\n"));
 	fprintf(output, _("  \\dv[S+] [PATTERN]      list views\n"));
 	fprintf(output, _("  \\dx[+]  [PATTERN]      list extensions\n"));
-	fprintf(output, _("  \\dy     [PATTERN]      list event triggers\n"));
+	fprintf(output, _("  \\dy[+]  [PATTERN]      list event triggers\n"));
 	fprintf(output, _("  \\l[+]   [PATTERN]      list databases\n"));
 	fprintf(output, _("  \\sf[+]  FUNCNAME       show a function's definition\n"));
 	fprintf(output, _("  \\sv[+]  VIEWNAME       show a view's definition\n"));