systemd: rename required AUTOFS4_FS to AUTOFS_FS

The `AUTOFS4_FS` name appears to be a legacy naming stub:

>Ok, I ran the script, and also decided that we might as well remove
>the AUTOFS4 legacy naming stub entry by now.
>
>It has been five years, and people will have either picked up the new
>name with 'make oldconfig', or they just don't use 'make oldconfig' at
>all.

https://lore.kernel.org/lkml/CAHk-=wgK9-Tx4BxYMrc0pg==mcaz3cjWF6-CBwVpM_BZAmf4JQ@mail.gmail.com/#r

That has been remove in 6.6 kernel and results in a failure:
```
error:
Failed assertions:
- CONFIG_AUTOFS4_FS is not enabled!
```

Signed-off-by: Jakub Sokołowski <jakub@status.im>

Changed files
+1 -1
nixos
modules
system
+1 -1
nixos/modules/system/boot/systemd.nix
···
system.requiredKernelConfig = map config.lib.kernelConfig.isEnabled
[ "DEVTMPFS" "CGROUPS" "INOTIFY_USER" "SIGNALFD" "TIMERFD" "EPOLL" "NET"
"SYSFS" "PROC_FS" "FHANDLE" "CRYPTO_USER_API_HASH" "CRYPTO_HMAC"
-
"CRYPTO_SHA256" "DMIID" "AUTOFS4_FS" "TMPFS_POSIX_ACL"
+
"CRYPTO_SHA256" "DMIID" "AUTOFS_FS" "TMPFS_POSIX_ACL"
"TMPFS_XATTR" "SECCOMP"
];