fixed typo

Author: danney-chun

CHANGELOG.md

@@ -3,7 +3,7 @@
 ## v3.1.15 (MAY 31, 2022)
 - Fixed bug TypingStatusUpdate event does not work in GroupChannelCollection.
 - Fixed Wrong Type definition in SendBird.d.ts
-- Fixed bug Android file upload if not working(RN)
+- Fixed bug Android file upload is not working(RN)
 ## v3.1.14 (MAY 20, 2022)
 - Fixed bug SessionHandlers Broken.
 

README.md

@@ -347,4 +347,4 @@ If you want to check the record of other versions, go to [Change Log](https://gi
 
 - Fixed bug TypingStatusUpdate event does not work in GroupChannelCollection.
 - Fixed Wrong Type definition in SendBird.d.ts
-- Fixed bug Android file upload if not working(RN)
+- Fixed bug Android file upload is not working(RN)