Remove redundant prototypes for SQL callable functions.

These aren't needed after 352a24a1f9d6. The remaining prototypes are
not defined on the SQL level.

Author: Andres Freund
Discussion: https://postgr.es/m/20190803193733.g3l3x3o42uv4qj7l@alap3.anarazel.de

src/include/catalog/pg_publication.h

@@ -92,6 +92,5 @@ extern ObjectAddress publication_add_relation(Oid pubid, Relation targetrel,
 extern Oid	get_publication_oid(const char *pubname, bool missing_ok);
 extern char *get_publication_name(Oid pubid, bool missing_ok);
 
-extern Datum pg_get_publication_tables(PG_FUNCTION_ARGS);
 
 #endif							/* PG_PUBLICATION_H */

src/include/executor/nodeAgg.h

@@ -311,6 +311,4 @@ extern void ExecReScanAgg(AggState *node);
 
 extern Size hash_agg_entry_size(int numAggs);
 
-extern Datum aggregate_dummy(PG_FUNCTION_ARGS);
-
 #endif							/* NODEAGG_H */