Remove redefinition of MlKemKey

Removes the redundant typedef of MlKemKey which will break builds on
pre-C11 compilers. KyberKey is defined as a macro for MlKemKey.

wolfssl/wolfcrypt/wc_mlkem.h

@@ -146,9 +146,6 @@ struct MlKemKey {
     extern "C" {
 #endif
 
-/* For backward compatibility */
-typedef struct MlKemKey KyberKey;
-
 WOLFSSL_LOCAL
 void mlkem_init(void);