default or selected kernelversion does not have config value CONFIG_NFSD_FAULT_INJECTION.
Result is shown for kernelversion 6.9.5

NFS server manual fault injection

configname: CONFIG_NFSD_FAULT_INJECTION

Linux Kernel Configuration
└─>File systems
└─>Network File Systems
└─>NFS server manual fault injection
In linux kernel since version 3.1 (release Date: 2011-10-24)  
This option enables support for manually injecting faults
into the NFS server. This is intended to be used for
testing error recovery on the NFS client.

If unsure, say N.