Update Puma to version 6.3

Fixes the error "Puma 5 is not compatible with Rack 3, please upgrade to Puma 6 or higher."

spec/support/echo_server.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'puma'
+require 'logger'
 require 'puma/binder'
 require 'puma/events'
 
@@ -26,18 +27,19 @@ class EchoServer
   def log(*args); end
 
   def listen(port)
-    events = Puma::Events.new(StringIO.new, StringIO.new)
-    binder = Puma::Binder.new(events)
-    binder.parse(["tcp://0.0.0.0:#{port}"], self)
+    # Instead of logging to the stdout/stderr, we'll log to a StringIO to prevent cluttering the test output
+    silent_stream = StringIO.new
+    logger = Puma::LogWriter.new(silent_stream, silent_stream)
+    events = Puma::Events.new
+    binder = Puma::Binder.new(logger)
+    binder.parse(["tcp://0.0.0.0:#{port}"], logger)
+
     @server = Puma::Server.new(self, events)
     @server.binder = binder
     @server.run
   end
 
   def stop
-    case @server
-    when Puma::Server then @server.stop(true)
-    else @server.stop
-    end
+    @server&.stop(true)
   end
 end