Remove prototype for nonexistent function.

src/bin/pg_dump/pg_dump.h

@@ -524,7 +524,6 @@ extern void simple_string_list_append(SimpleStringList *list, const char *val);
 extern bool simple_oid_list_member(SimpleOidList *list, Oid val);
 extern bool simple_string_list_member(SimpleStringList *list, const char *val);
 
-extern void check_conn_and_db(void);
 extern void exit_nicely(void);
 
 extern void parseOidArray(const char *str, Oid *array, int arraysize);