Reduce visibility of JSIModuleRegistry. (#39740)

Summary:
Pull Request resolved: #39740

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 JSIModuleRegistry.

Reviewed By: RSNara

Differential Revision: D49752138

fbshipit-source-id: c36deaaf6c6796159258f33afc15cea821b490f0

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

@@ -12,7 +12,7 @@
 import java.util.List;
 import java.util.Map;
 
-public class JSIModuleRegistry {
+class JSIModuleRegistry {
 
   private final Map<JSIModuleType, JSIModuleHolder> mModules = new HashMap<>();