[ruby/irb] Fix a typo (https://github.com/ruby/irb/pull/912)

https://github.com/ruby/irb/commit/2057248e40

lib/irb/cmd/nop.rb

@@ -1,4 +1,4 @@
 # frozen_string_literal: true
 
 # This file is just a placeholder for backward-compatibility.
-# Please require 'irb' and inheirt your command from `IRB::Command::Base` instead.
+# Please require 'irb' and inherit your command from `IRB::Command::Base` instead.