Move internal modifier to the object to work around this build error

```
E:\AndroidStudioProjects\nowinandroid\core\datastore\build\generated\ksp\demoDebug\java\com\google\samples\apps\nowinandroid\core\datastore\di\DataStoreModule_ProvidesUserPreferencesDataStore$datastore_demoDebugFactory.java:71: error: cannot find symbol
    return Preconditions.checkNotNullFromProvides(DataStoreModule.INSTANCE.providesUserPreferencesDataStore$datastore_demoDebug(context, ioDispatcher, scope, userPreferencesSerializer));
                                                                          ^
  symbol:   method providesUserPreferencesDataStore$datastore_demoDebug(Context,CoroutineDispatcher,CoroutineScope,UserPreferencesSerializer)
  location: variable INSTANCE of type DataStoreModule
```

core/datastore/src/main/kotlin/com/google/samples/apps/nowinandroid/core/datastore/di/DataStoreModule.kt

@@ -37,11 +37,11 @@ import javax.inject.Singleton
 
 @Module
 @InstallIn(SingletonComponent::class)
-object DataStoreModule {
+internal object DataStoreModule {
 
     @Provides
     @Singleton
-    internal fun providesUserPreferencesDataStore(
+    fun providesUserPreferencesDataStore(
         @ApplicationContext context: Context,
         @Dispatcher(IO) ioDispatcher: CoroutineDispatcher,
         @ApplicationScope scope: CoroutineScope,