[ROSAPPS:SYSUTILS] Remove remnant config.h (reactos#8075)

- `REACTOS_NO_SECURITY_SS`
Added on 9ef17ea (r475), without being used.
Not currently used either.

- `FMIFS_IMPORT_DLL`
Now lives in the 2 /base programs which use it.
Addendum to (probably earlier than) 9723b5e (r70868) and dc17af9 (r70916).

Author: SergeGautherie