Remove kex.c from kyber768 nmake file

crypto_kem/kyber768/clean/Makefile.Microsoft_nmake

@@ -2,7 +2,7 @@
 #    nmake /f Makefile.Microsoft_nmake
 
 LIB=libkyber768_clean.lib
-OBJECTS=cbd.obj indcpa.obj kem.obj kex.obj ntt.obj poly.obj polyvec.obj precomp.obj reduce.obj verify.obj
+OBJECTS=cbd.obj indcpa.obj kem.obj ntt.obj poly.obj polyvec.obj precomp.obj reduce.obj verify.obj
 
 CFLAGS=/I ..\..\..\common /W1 /WX # FIXME: ideally would use /W4 instead of /W1, but too many failures in Kyber right now