BUG #16946: It may be that the content of the document is missing

The following bug has been logged on the website:

Bug reference: 16946
Logged by: 强 魏
Email address: 1726002692(at)qq(dot)com
PostgreSQL version: 13.2
Operating system: centos
Description:

No information about the function pg_get_function_arg_default was found in
the official manual.
user:postgres(at)db:postgres[[local]:5432]#select version();
+-----------------------------------------------------------------------------+
| version
|
+-----------------------------------------------------------------------------+
| PostgreSQL 13.2 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 7.3.0,
64-bit |
+-----------------------------------------------------------------------------+
(1 row)

Time: 0.664 ms
user:postgres(at)db:postgres[[local]:5432]#\df pg_get_function_arg_default
List of functions
+------------+-----------------------------+------------------+---------------------+------+
| Schema | Name | Result data type | Argument
data types | Type |
+------------+-----------------------------+------------------+---------------------+------+
| pg_catalog | pg_get_function_arg_default | text | oid, integer
| func |
+------------+-----------------------------+------------------+---------------------+------+
(1 row)