Fix KYBER_decap declaration

I missed a spot in adding all the length hints. (Only the definition had
it, not the declaration.) Thanks to Alex Gaynor for reporting this.

Change-Id: I79e46845aded6ddaae7b5bbb578876f47fb80a5e
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/64427
Reviewed-by: Alex Gaynor <alex.gaynor@gmail.com>
Auto-Submit: David Benjamin <davidben@google.com>
Commit-Queue: Adam Langley <agl@google.com>
Reviewed-by: Adam Langley <agl@google.com>

include/openssl/kyber.h

diff --git a/include/openssl/kyber.h b/include/openssl/kyber.h
index 9f5a3ca..e0268fc 100644
--- a/include/openssl/kyber.h
+++ b/include/openssl/kyber.h
@@ -91,7 +91,7 @@
 // authenticated encryption scheme in order to discover the decapsulation
 // failure.
 OPENSSL_EXPORT void KYBER_decap(
-    uint8_t *out_shared_secret,
+    uint8_t out_shared_secret[KYBER_SHARED_SECRET_BYTES],
     const uint8_t ciphertext[KYBER_CIPHERTEXT_BYTES],
     const struct KYBER_private_key *private_key);