fix

index.bs

@@ -795,7 +795,7 @@ sequence<{{WebTransportHash}}> |serverCertificateHashes|, run these steps.
      |serverCertificateHashes| is specified instead of the default certificate version algorithm,
      validate the certificate against [=custom certificate requirements=], and then
      [=verify a certificate hash|verify the certificate hash=] against |serverCertificateHashes|.
-     The certificate is considered valid only if both of those checks pass.
+     The certificate is considered valid if and only if both of those checks pass.
   1. If |connection| is failure, then abort the remaining steps and [=queue a network task=] with
      |transport| to run these steps:
     1. If |transport|.{{[[State]]}} is `"closed"` or `"failed"`, then abort these steps.