Validate buffer size as Integer instead of Numeric

Change concurrent_component_streaming_buffer_size validation to require
Integer instead of Numeric. Buffer sizes represent discrete queue capacity
counts and should not accept float values like 64.5.

This provides better type safety and clearer error messages for users who
might accidentally pass non-integer values.

Addresses CodeRabbit feedback.

Author: ihabadham

react_on_rails_pro/lib/react_on_rails_pro/configuration.rb

@@ -211,11 +211,11 @@ def validate_remote_bundle_cache_adapter
     end
 
     def validate_concurrent_component_streaming_buffer_size
-      return if concurrent_component_streaming_buffer_size.is_a?(Numeric) &&
+      return if concurrent_component_streaming_buffer_size.is_a?(Integer) &&
                 concurrent_component_streaming_buffer_size.positive?
 
       raise ReactOnRailsPro::Error,
-            "config.concurrent_component_streaming_buffer_size must be set and must be a positive number"
+            "config.concurrent_component_streaming_buffer_size must be a positive integer"
     end
 
     def setup_renderer_password