default or selected kernelversion does not have config value CONFIG_LIB80211_CRYPT_WEP.
Result is shown for kernelversion 6.9.9

CONFIG_LIB80211_CRYPT_WEP (not configurable)

modulename: lib80211_crypt_wep.ko

configname: CONFIG_LIB80211_CRYPT_WEP

Linux Kernel Configuration
└─>Networking support
└─>Wireless
└─>LIB80211_CRYPT_WEP
In linux kernel since version 2.6.29 (release Date: 2009-03-23)  
source code:
net/wireless/lib80211_crypt_wep.c