Remove duplicated GUC names in unsync_guc_name.h
Fixes
"autovacuum_analyze_threshold",
"autovacuum_freeze_max_age",
"autovacuum_max_workers",
- "autovacuum_max_workers",
"autovacuum_multixact_freeze_max_age",
"autovacuum_naptime",
"autovacuum_vacuum_cost_delay",
"cpu_tuple_cost",
"create_restartpoint_on_ckpt_record_replay",
"cursor_tuple_fraction",
- "cursor_tuple_fraction",
"data_checksums",
"data_directory",
"db_user_namespace",
"event_source",
"exit_on_error",
"external_pid_file",
- "external_pid_file",
"extra_float_digits",
"from_collapse_limit",
"fsync",
"gp_enable_hashjoin_size_heuristic",
"gp_enable_interconnect_aggressive_retry",
"gp_enable_minmax_optimization",
- "gp_enable_minmax_optimization",
"gp_enable_motion_deadlock_sanity",
"gp_enable_multiphase_agg",
"gp_enable_predicate_propagation",
