Add CryptographicException to docs of GetCertContentType

Author: vcsjones

xml/System.Security.Cryptography.X509Certificates/X509Certificate2.xml

@@ -2047,6 +2047,7 @@ The certificate is encoded according to the IETF RFC 7468 "strict"
         </remarks>
         <exception cref="T:System.ArgumentException">
           <paramref name="rawData" /> has a zero length or is <see langword="null" />.</exception>
+        <exception cref="T:System.Security.Cryptography.CryptographicException">The type of contents in <paramref name="rawData" /> could not be determined or is unknown.</exception>
       </Docs>
     </Member>
     <Member MemberName="GetCertContentType">