Rename Function Lambda parameter to match command interface in (Default) ReactiveXxxOperations

[jxblum]

In all (Default) ReactiveXxxOperation interfaces used by ReactiveRedisTemplate, the (Redis) operation methods refer to their corresponding command interface as "connection" when passing the Function Lambda to the createMono(:Function<..>, Publisher<T>) or createFlux(:Function<..>, Publisher<T>) methods, which is not technically accurate, and confusing.

The Function Lambda expects an instance of reactive commands (e.g. ReactiveSetCommands in the (Default) ReactiveSetOperations interface), which is obtained from the ReactiveRedisConnection.