Fix a typo

The method that overrides `Methods::RESOURCES_READ` is named `resources_read_handler`,
not `read_resource_handler`:
https://github.com/modelcontextprotocol/ruby-sdk/blob/18f3e87/lib/model_context_protocol/server.rb#L97-L99

Author: koic

lib/model_context_protocol/server.rb

@@ -252,7 +252,7 @@ def list_resources(request)
       @resources.map(&:to_h)
     end
 
-    # Server implementation should set read_resource_handler to override no-op default
+    # Server implementation should set `resources_read_handler` to override no-op default
     def read_resource_no_content(request)
       add_instrumentation_data(method: Methods::RESOURCES_READ)
       add_instrumentation_data(resource_uri: request[:uri])