Revoke CREATE for a user from Google Cloud SQL Postgres?

Question

I'm using Google Cloud SQL Postgres and having difficulty revoking privileges to create tables from a user.

I first removed all roles and attributes from the user (truncated for brevity):

mydatabase=> \du+
                                                             List of roles
         Role name         |                         Attributes                         |           Member of            | Description
---------------------------+------------------------------------------------------------+--------------------------------+-------------
 cloudsqlsuperuser         | Create role, Create DB                                     | {pg_monitor,pg_signal_backend} |
 myuser                    |                                                            | {}                             |
 postgres                  | Create role, Create DB                                     | {cloudsqlsuperuser}            |

This worked for preventing the user from accessing data in existing tables, but the user was still able to create new tables. I figured this might be because of the default CREATE privilege PUBLIC has to the public schema so I tried revoking both that and any specific privileges for the user...

postgres=> REVOKE CREATE ON SCHEMA public FROM PUBLIC;
REVOKE
postgres=> REVOKE ALL ON DATABASE "mydatabase" FROM "myuser";
REVOKE
postgres=> REVOKE ALL ON SCHEMA public FROM myuser;
REVOKE

But the user still has access to CREATE tables within mydatabase:

mydatabase=> SELECT pg_catalog.has_schema_privilege('myuser', 'public', 'CREATE');
 has_schema_privilege
----------------------
 t
(1 row)

I thought maybe the issue was that the permissions were at the database level and not the schema level so I tried revoking them there as well, but no luck:

postgres=> GRANT ALL ON DATABASE "mydatabase" TO cloudsqlsuperuser;
GRANT
postgres=> GRANT ALL ON DATABASE "mydatabase" TO postgres;
GRANT
postgres=> REVOKE ALL ON DATABASE "mydatabase" FROM myuser;
REVOKE
postgres=> REVOKE ALL ON DATABASE "mydatabase" FROM public;
REVOKE
postgres=> GRANT CONNECT ON DATABASE "mydatabase" TO myuser;
GRANT

The output of \dn+ doesn't show any other permissions that should affect this user AFAIK:

postgres=> \dn+
                                       List of schemas
  Name  |       Owner       |           Access privileges            |      Description
--------+-------------------+----------------------------------------+------------------------
 public | cloudsqlsuperuser | cloudsqlsuperuser=UC/cloudsqlsuperuser+| standard public schema
        |                   | =U/cloudsqlsuperuser                  +|
        |                   | postgres=C/cloudsqlsuperuser           |
(1 row)

Additionally, the search_path is default:

postgres=> SHOW search_path;
   search_path
-----------------
 "$user", public
(1 row)

How do I correctly remove the CREATE privilege for this user?