Similar to ZBX-22868, but not sure it fixed for Redis also.
Steps to reproduce:

1. Check document
   https://www.zabbix.com/documentation/6.4/en/manual/appendix/config/zabbix_agent2_plugins/redis_plugin
   
2. add redis password only to the configuration file /etc/zabbix/zabbix_agent2.d/plugins.d/redis.conf:

Plugins.Redis.Sessions.Redis.Password=*****

1. Upgrade zabbix-agent2 to version 6.4.3
2. Check item redis.ping[Redis], for example.

Result:
Item became unsupported with error 'host is required'.
Expected:
'tcp://localhost:6379' as Default URI for connecting to Redis; used if no value is specified in an item key or named session.