Flush the Lua scripts cache.

Please refer to the `EVAL` documentation for detailed information about Redis Lua scripting.

By default, `SCRIPT FLUSH` will synchronously flush the cache.
Starting with Redis 6.2, setting the **lazyfree-lazy-user-flush** configuration directive to "yes" changes the default flush mode to asynchronous.

It is possible to use one of the following modifiers to dictate the flushing mode explicitly:

* `ASYNC`: flushes the cache asynchronously
* `!SYNC`: flushes the cache synchronously

@return

@simple-string-reply

@history

* `>= 6.2.0`: Added the `ASYNC` and `!SYNC` flushing mode modifiers, as well as the  **lazyfree-lazy-user-flush** configuration directive.
