psql: have \d show FKs on partitioned tables

Commit 3de241db missed to update psql to display foreign keys on
partitioned tables.  Add that.

Reported-by: Amit Langote
Author: Amit Langote
Reviewed-by: Álvaro Herrera
Discussion: https://postgr.es/m/a66879e5-636f-d4dd-b4a4-92bdca5a828f@lab.ntt.co.jp

src/bin/psql/describe.c

@@ -2311,8 +2311,13 @@ describeOneTableDetails(const char *schemaname,
 			PQclear(result);
 		}
 
-		/* print foreign-key constraints (there are none if no triggers) */
-		if (tableinfo.hastriggers)
+		/*
+		 * Print foreign-key constraints (there are none if no triggers,
+		 * except if the table is partitioned, in which case the triggers
+		 * appear in the partitions)
+		 */
+		if (tableinfo.hastriggers ||
+			tableinfo.relkind == RELKIND_PARTITIONED_TABLE)
 		{
 			printfPQExpBuffer(&buf,
 							  "SELECT conname,\n"