spec has been deprecated, use struct

Author: JaredCE

src/definitionGenerator.js

@@ -81,7 +81,7 @@ class DefinitionGenerator {
       this.REDOCLY_RULES = require(path.resolve("options", "redocly.json"));
     } catch (err) {
       this.REDOCLY_RULES = {
-        spec: "error",
+        struct: "error",
         "path-parameters-defined": "error",
         "operation-2xx-response": "error",
         "operation-4xx-response": "error",

test/helpers/redocly.json

@@ -1,4 +1,4 @@
 {
-  "spec": "error",
+  "struct": "error",
   "operation-2xx-response": "warn"
 }