Issue with Amazon Aurora PostgreSQL Database Upgrade using pg_upgrade v13 to v14 or 15v

I'm encountering difficulties while trying to upgrade my Amazon Aurora PostgreSQL database from version 13 to version 15 using the pg_upgrade utility. The upgrade process is failing with an error, and I need assistance to resolve this issue.

Error Message:

pg_restore: creating FUNCTION "public.rds_get_stat_connections_counters()"
pg_restore: while PROCESSING TOC:
pg_restore: from TOC entry 225; 1255 2922011 FUNCTION rds_get_stat_connections_counters() rdsadmin
pg_restore: error: could not execute query: ERROR:  could not find function "rds_get_stat_connections_counters" in file "/rdsdbbin/aurora-15.5.15.5.0.21262.0/lib/postgresql/rdsutils.so"
Command was: CREATE FUNCTION "public"."rds_get_stat_connections_counters"(OUT "dbid" "oid", OUT "db_name" "text", OUT "rolid" "oid", OUT "role_name" "text", OUT "application_name" "text", OUT "ssl" "text", OUT "auth" "text", OUT "client_addr" "text", OUT "authorized" integer, OUT "not_authorized" integer, OUT "total_auth_failed" integer, OUT "bad_db_name" integer, OUT "bad_db_oid" integer, OUT "bad_db_perm" integer, OUT "bad_conn_packet" integer, OUT "startup_packet_timeout" integer, OUT "lastattempt" timestamp with time zone) RETURNS SETOF "record"
    LANGUAGE "c" STRICT
    AS '$libdir/rdsutils', 'rds_get_stat_connections_counters';

Steps Taken So Far: Ensured that I have taken a full backup of my database before initiating the upgrade. Verified the compatibility of extensions and custom functions with PostgreSQL version 15.

Your prompt attention and assistance are greatly appreciated.