Removed client engine validation

## Summary
Removed Client engine validation in the SDK to allow tracking events from new clients without friction.

## Test plan
- Manually Tested
- All tests pass

Author: zashraf1985

packages/optimizely-sdk/lib/optimizely/index.ts

@@ -85,7 +85,7 @@ export default class Optimizely {
 
   constructor(config: OptimizelyOptions) {
     let clientEngine = config.clientEngine;
-    if (enums.VALID_CLIENT_ENGINES.indexOf(clientEngine) === -1) {
+    if (!clientEngine) {
       config.logger.log(
         LOG_LEVEL.INFO,
         LOG_MESSAGES.INVALID_CLIENT_ENGINE,

packages/optimizely-sdk/lib/optimizely_user_context/index.ts

@@ -28,8 +28,6 @@ import {
 } from '../../lib/shared_types';
 import { DECISION_MESSAGES, LOG_MESSAGES } from '../utils/enums';
 
-const MODULE_NAME = 'OPTIMIZELY_USER_CONTEXT';
-
 const logger = getLogger();
 
 export default class OptimizelyUserContext {

packages/optimizely-sdk/lib/utils/enums/index.tests.js

@@ -183,14 +183,6 @@ export const REACT_NATIVE_CLIENT_ENGINE = 'react-native-sdk';
 export const REACT_NATIVE_JS_CLIENT_ENGINE = 'react-native-js-sdk';
 export const NODE_CLIENT_VERSION = '4.8.0-beta';
 
-export const VALID_CLIENT_ENGINES = [
-  NODE_CLIENT_ENGINE,
-  REACT_CLIENT_ENGINE,
-  JAVASCRIPT_CLIENT_ENGINE,
-  REACT_NATIVE_CLIENT_ENGINE,
-  REACT_NATIVE_JS_CLIENT_ENGINE,
-];
-
 export const NOTIFICATION_TYPES = notificationTypesEnum;
 
 export const DECISION_NOTIFICATION_TYPES = {