cryptographic-message-syntax: box large enum variant

I guess it isn't used because this didn't introduce any compile
errors.

cryptographic-message-syntax/src/asn1/rfc5652.rs

@@ -1104,7 +1104,7 @@ impl RevocationInfoChoices {
 /// ```
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub enum RevocationInfoChoice {
-    Crl(CertificateList),
+    Crl(Box<CertificateList>),
     Other(OtherRevocationInfoFormat),
 }