Remove outdated comment in ECDSA implementation.

As of https://boringssl-review.googlesource.com/26968, digest_to_scalar
should output a fully-reduced value.

Change-Id: I9fccc62413b17184eb3aa6fa5cd87d7e7849e2eb
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/50325
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: David Benjamin <davidben@google.com>

crypto/fipsmodule/ecdsa/ecdsa.c

@@ -68,8 +68,7 @@
 
 
 // digest_to_scalar interprets |digest_len| bytes from |digest| as a scalar for
-// ECDSA. Note this value is not fully reduced modulo the order, only the
-// correct number of bits.
+// ECDSA.
 static void digest_to_scalar(const EC_GROUP *group, EC_SCALAR *out,
                              const uint8_t *digest, size_t digest_len) {
   const BIGNUM *order = &group->order;