fcl-base: blowfish2: Remove unnecessary destructor from TBlowFish2Stream

Summary

The only operation in the TBlowFish2Stream destructor is calling FreeAndNil for a property, which type is not a TObject descendant but a record. That leads to an Access Violation. FreeAndNil call is not needed, therefore the whole destructor can be removed.

What is the current bug behavior?

Calling a destructor on either encrypting or decrypting stream always results in an Access Violation.

What is the behavior after applying this patch?

Blowfish2 streams can be disposed properly.