Remove old NFS environments.

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SRE Support Needed As part of scalability#2683 (comment 1696244453) we discovered that we still have NFS set up in the following environments:

• All the staging ones have 10.142.0.53:/mnt/gitlab-nfs mounted in the staging-ref-3k-hybrid-us cluster, and seems to be pretty broadly mounted.

• All the pre ones have 10.237.0.2:/storage mounted and on three host types: gitaly, praefect, and deploy.

As far as we're all aware, this shouldn't actually exist any longer, and we should clean this up.