[FIXUP] Correct docs and drop server level protocol version

Author: sambostock

README.md

@@ -240,18 +240,22 @@ config.instrumentation_callback = ->(data) {
 
 ### Server Protocol Version
 
-The server's protocol version can be overridden using the `protocol_version` class method:
+The server's protocol version can be overridden via the `Configuration#protocol_version` method:
 
 <!-- SNIPPET ID: set_server_protocol_version -->
 ```ruby
-MCP::Server.protocol_version = "2024-11-05"
+MCP.configure do |config|
+  config.protocol_version = "2024-11-05"
+end
 ```
 
 This will make all new server instances use the specified protocol version instead of the default version. The protocol version can be reset to the default by setting it to `nil`:
 
 <!-- SNIPPET ID: unset_server_protocol_version -->
 ```ruby
-MCP::Server.protocol_version = nil
+MCP.configure do |config|
+  config.protocol_version = nil
+end
 ```
 
 Be sure to check the [MCP spec](https://spec.modelcontextprotocol.io/specification/2024-11-05/) for the protocol version to understand the supported features for the version being set.

lib/mcp/server.rb

@@ -9,14 +9,6 @@ module MCP
   class Server
     DEFAULT_VERSION = "0.1.0"
 
-    class << self
-      def protocol_version = MCP.configuration.protocol_version
-
-      def protocol_version=(version)
-        MCP.configuration.protocol_version = version
-      end
-    end
-
     class RequestHandlerError < StandardError
       attr_reader :error_type
       attr_reader :original_error

test/fixtures/files/code_snippet_wrappers/readme/set_server_protocol_version.rb

@@ -4,4 +4,4 @@
 
 require_relative "code_snippet"
 
-puts MCP::Server.protocol_version
+puts MCP.configuration.protocol_version