Remove unused C structure member

Remove quote_all_identifiers from struct _dumpOptions.

Discussion: https://postgr.es/m/d3d92ce9-78a4-8adb-0393-d3deeec29f7e@postgrespro.ru

Author: Arthur Zakirov

Backpatch-through: head

src/bin/pg_dump/pg_backup.h

@@ -153,7 +153,6 @@ typedef struct _dumpOptions
 	int			no_synchronized_snapshots;
 	int			no_unlogged_table_data;
 	int			serializable_deferrable;
-	int			quote_all_identifiers;
 	int			disable_triggers;
 	int			outputNoTablespaces;
 	int			use_setsessauth;