Serialised ImageService2 should have no type

[donaldgray]

Single item and named-query manifests that serialise ImageService2 resources always include the @type value of "ImageService2", e.g.

"service": {
  "@context": "http://iiif.io/api/image/2/context.json",
  "@id": "https://dlc.services/thumbs/1/2/foo",
  "@type": "ImageService2",
  "profile": "http://iiif.io/api/image/2/level0.json",
  "sizes": [

However, this value is incorrect as per documentation:

`@type | Optional | The type for the Image. If present, the value must be the string iiif:Image.

Given the above we can either omit it or make it "iiif:Image" as "ImageService2" wasn't introduced until v3 but only when rendering on a Presentation2 manifest.

This may require an update to the https://github.com/digirati-co-uk/iiif-net nuget package and/or an update to DLCS.

[donaldgray]

@griffri - I'd missed this on above requirement but "type" on IIIF Image2 info.json files shouldn't be ImageService2 either. However, rather than omit we should set this to iiif:Image