[BUG] Remove prestop to delete csi socket

[cheyang]

What is your environment(Kubernetes version, Fluid version, etc.)

Describe the bug

The following logic is useless, please remove it.

preStop:
              exec:
                command: ["/bin/sh", "-c", "rm -rf /registration/fluid /registration/fuse.csi.fluid.io-reg.sock"]

What you expect to happen:

How to reproduce it

Additional Information