minor rewording re application of type-scoped contexts

[VladimirAlexiev]

In Scoped Contexts, the description of Type-Scoped Contexts has two notes (right after this note):

When expanding, each value of @type is considered (in code point order) where that value is also a term in the active context having its own type-scoped context. If so, that the scoped context is applied to the active context.

The values of @type are unordered, so if multiple types are listed, the order that type-scoped contexts are applied is based on code point ordering

I suggest to merge these two notes and make it more explicit that later contexts override earlier contexts;
and add a last sentence to say explicitly that @type must be present in the JSON-LD instance for type-scoped contexts to work:

When expanding, each value of @type is considered. If the value is also a term in the active context having its own type-scoped context, the scoped context is applied to the active context. If multiple @type types are present they are applied in code point order (since the values of @type are unordered), and terms defined in later scoped contexts take precedence. If no @type is present then no type-scoped contexts are applied.