Fix a typo in comment

Reviewed-by: NRichard Levitte <levitte@openssl.org>
Reviewed-by: NPaul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/4949)

crypto/ec/ecdsa_ossl.c

@@ -298,7 +298,7 @@ ECDSA_SIG *ossl_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len,
         }
         if (BN_is_zero(s)) {
             /*
-             * if kinv and r have been supplied by the caller don't to
+             * if kinv and r have been supplied by the caller, don't
              * generate new kinv and r values
              */
             if (in_kinv != NULL && in_r != NULL) {