message: Fix link to MAC documentation
diff: @@ -364,7 +364,7 @@ to encrypt or decrypt data streams:
  ### Message Authentication Code
  The following snippets shows how to compute or verify a [MAC (Message Authentication
  -Code)](RIMITIVES.md#message-authentication-code):
  +Code)](PRIMITIVES.md#message-authentication-code):
  ```java
  import com.google.crypto.tink.KeysetHandle;
  