Fix documentation missed in 82f9853.

82f9853 replaced ssl_seal_align_prefix_len with two functions,
tls_seal_align_prefix_len and dtls_seal_align_prefix_len. This change
updates documentation that referred to the old ssl_seal_align_prefix_len
function to refer to the correct function.

Change-Id: Ieb8891eff03efc3d894aa56729ae6e47f4be3288
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/70207
Commit-Queue: Bob Beck <bbe@google.com>
Reviewed-by: Bob Beck <bbe@google.com>
Auto-Submit: Nick Harper <nharper@chromium.org>

ssl/internal.h

@@ -1028,7 +1028,7 @@ bool ssl_needs_record_splitting(const SSL *ssl);
 // 1/n-1 record splitting and may write two records concatenated.
 //
 // For a large record, the bulk of the ciphertext will begin
-// |ssl_seal_align_prefix_len| bytes into out. Aligning |out| appropriately may
+// |tls_seal_align_prefix_len| bytes into out. Aligning |out| appropriately may
 // improve performance. It writes at most |in_len| + |SSL_max_seal_overhead|
 // bytes to |out|.
 //