Cleanup clang compiler warnings

Summary:
Cleanup clang compiler warnings.
The last version delete some variables that still used in code.
Fix the problem and try to launch again.

Reviewed By: hershi

Differential Revision: D8704442

fbshipit-source-id: 8bd37fc9f2b27104fe15c4c8b8323e2bfd8c1060

ReactAndroid/src/main/jni/react/jni/CatalystInstanceImpl.cpp

@@ -42,7 +42,6 @@ namespace {
 
 class Exception : public jni::JavaClass<Exception> {
  public:
-  static auto constexpr kJavaDescriptor = "Ljava/lang/Exception;";
 };
 
 class JInstanceCallback : public InstanceCallback {