Remove serializer-related productions

[tobie]

Dear all,

In whatwg/webidl#323, we removed serializers from WebIDL and replaced it with regular toJSON operations (and the new [Default] extended attribute).

This means that we were able to remove all of the serializer-related productions from the WebIDL grammar. And in particular the following non-terminals:

• Serializer
  • Serializer was also removed from the rhs expression of InterfaceMember.
• SerializerRest
• OperationRest
• SerializationPattern
• SerializationPatternMap
• SerializationPatternList

and the following terminals:

• serializer in ArgumentNameKeyword.

Because we're relying on existing grammar for the replacement solution (operations and extended attributes), there is no new grammar to support. 💃

As usual, please feel free to reach out if anything needs clarification or if you have questions.

Thanks!