jaxrs-resteasy: fix outer enum case

[jmini]

With the jaxrs-resteasy generator, this PR fixes the outer-class enum case.

Example OAS3:

openapi: 3.0.1
info:
  title: ping test
  version: '1.0'
servers:
  - url: 'http://localhost:8000/'
paths:
  /ping:
    get:
      operationId: pingGet
      responses:
        '200':
          description: Ok
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ObjWithEnums'

components:
  schemas:
    ObjWithEnums:
      type: object
      properties:
        SProp:
            $ref: "#/components/schemas/StringEnum"

    StringEnum:
      type: string
      enum:
        - "c"
        - "b"
        - "a"

[jmini]

Without the change, the generated code does not compile. After the fix, the diff looks like this:

diff --git a/openapi-generator-utils/treepots/treepots-openapigen-jaxrs-resteasy/src/gen/java/org/openapitools/model/StringEnum.java b/openapi-generator-utils/treepots/treepots-openapigen-jaxrs-resteasy/src/gen/java/org/openapitools/model/StringEnum.java
index 24701bf..27243c0 100644
--- a/src/gen/java/org/openapitools/model/StringEnum.java
+++ b/src/gen/java/org/openapitools/model/StringEnum.java
@@ -5,5 +5,5 @@ import java.util.ArrayList;
 import com.fasterxml.jackson.annotation.JsonValue;
 import javax.validation.constraints.*;
 public enum StringEnum {
-    {values=[c, b, a], enumVars=[{name=C, value="c"}, {name=B, value="b"}, {name=A, value="a"}]}
+    C, B, A
 }