Fix json schema definition

spec/ee/fixtures/api/schemas/public_api/v4/issues.json

 {
   "allOf": [
-    { "$ref": "../issues.json" },
+    { "$ref": "../../../../../../fixtures/api/schemas/public_api/v4/issues.json" },
     {
       "properties": {
         "weight": { "type": ["integer", "null"] }

spec/support/api/schema_matcher.rb

@@ -13,7 +13,7 @@ RSpec::Matchers.define :match_response_schema do |schema, dir: '', **options|
   end
 
   failure_message do |response|
-    "didn't match the schema defined by #{schema_path(schema)}" \
+    "didn't match the schema defined by #{SchemaPath.expand(schema, dir)}" \
     " The validation errors were:\n#{@errors.join("\n")}"
   end
 end