Reduce visibility of JSIModuleHolder

Summary:
In an attempt to reduce footprint of React Native Android public APIs we are reducing visibility of classes and interfaces that are not meant to be used publicly OR are public but have no usages.
As part of our analysis, which involved looking for usages inside the Meta codebase and code search in OSS, we've detected that this class/interface is public but it's not used from other packages.

If you are using this class or interface please comment in this PR and we will restate the public access.

changelog: [Android][Changed] Reducing visibility of JSIModuleHolder

Reviewed By: RSNara

Differential Revision: D49752136

fbshipit-source-id: 94148bcac920645fbb857e648e10330a72f481d6

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/bridge/JSIModuleHolder.java

@@ -7,7 +7,7 @@
 
 package com.facebook.react.bridge;
 
-public class JSIModuleHolder {
+class JSIModuleHolder {
 
   private JSIModule mModule;
   private final JSIModuleSpec mSpec;