Fix documentation string.

SSL_CTX_set_retain_only_sha256_of_client_certs's comment wasn't quite right.

Change-Id: I40527eebf2988d117cd8bd544bb5f16936c2cbfb
Reviewed-on: https://boringssl-review.googlesource.com/6982
Reviewed-by: Adam Langley <agl@google.com>

include/openssl/ssl.h

@@ -2897,9 +2897,9 @@ OPENSSL_EXPORT size_t SSL_get_server_random(const SSL *ssl, uint8_t *out,
  * NULL if one has not been negotiated yet or there is no pending handshake. */
 OPENSSL_EXPORT const SSL_CIPHER *SSL_get_pending_cipher(const SSL *ssl);
 
-/* SSL_CTX_retain_only_sha256_of_client_certs, on a server, sets whether only
- * the SHA-256 hash of peer's certificate should be saved in memory and in the
- * session. This can save memory, ticket size and session cache space. If
+/* SSL_CTX_set_retain_only_sha256_of_client_certs, on a server, sets whether
+ * only the SHA-256 hash of peer's certificate should be saved in memory and in
+ * the session. This can save memory, ticket size and session cache space. If
  * enabled, |SSL_get_peer_certificate| will return NULL after the handshake
  * completes. See the |peer_sha256| field of |SSL_SESSION| for the hash. */
 OPENSSL_EXPORT void SSL_CTX_set_retain_only_sha256_of_client_certs(SSL_CTX *ctx,