housekeeping: corresponding changes for swagger-api/swagger-editor#1935 (via #5170)

* `schema` -> `structural`

* drop strip-instance transformer

Author: shockey

src/core/plugins/err/error-transformers/hook.js

@@ -1,12 +1,10 @@
 import reduce from "lodash/reduce"
 import * as NotOfType from "./transformers/not-of-type"
 import * as ParameterOneOf from "./transformers/parameter-oneof"
-import * as StripInstance from "./transformers/strip-instance"
 
 const errorTransformers = [
   NotOfType,
-  ParameterOneOf,
-  StripInstance
+  ParameterOneOf
 ]
 
 export default function transformErrors (errors, system) {

src/core/plugins/err/error-transformers/transformers/parameter-oneof.js

@@ -38,7 +38,7 @@ function createTailoredParameterError(err, jsSpec) {
       message,
       path: err.get("path") + ".in",
       type: "spec",
-      source: "schema",
+      source: "structural",
       level: "error"
     })
   }
@@ -49,7 +49,7 @@ function createTailoredParameterError(err, jsSpec) {
       message,
       path: err.get("path") + ".collectionFormat",
       type: "spec",
-      source: "schema",
+      source: "structural",
       level: "error"
     })
   }