bump to 3.8.4+3

CHANGELOG.md

+# 3.8.4+3
+* Fix #478 #466 #470 #472
+
 # 3.8.4+2
 * Fix #471
 * 更换pod源

pubspec.yaml

 name: fluwx
 description: The capability of implementing WeChat SDKs in Flutter. With Fluwx, developers can use WeChatSDK easily, such as sharing, payment, lanuch mini program and etc.
-version: 3.8.4+2
+version: 3.8.4+3
 homepage: https://github.com/JarvanMo/fluwx
 
 environment: