Merged PR 10177217: Remove outdated security advice on RC4 comment

Per [this GitHub issue](https://github.com/microsoft/SymCrypt/issues/34), the advice on key generation for RC4 is outdated and no longer best practice. RC4 should never be used except for backwards compatibility, but this part of the comment is unhelpful in any case, so this PR removes it.

Thanks to [Myriachan](https://github.com/Myriachan) for reporting this issue.

inc/symcrypt.h

@@ -4833,7 +4833,6 @@ SymCryptRc4Init(
 // Initialize an RC4 encryption/decryption state.
 // WARNING: the most common error in using RC4 is to use the same key to encrypt two different pieces of data.
 // This is insecure and should never be done; you need a unique key for each data element that is encrypted.
-// Typically this is done by concatenating the key and a nonce or IV to generate the RC4 key.
 //
 
 VOID