✅ Fix typo in FakeServer (tests only)

Author: nevans

test/net/imap/fake_server/command_reader.rb

@@ -10,7 +10,7 @@ class CommandReader
 
     def initialize(socket)
       @socket = socket
-      @last_comma0 = nil
+      @last_command = nil
     end
 
     def get_command