removed a no longer needed TODO for the vulnerability i fixed

lib/landline/extensions/session.rb

@@ -75,9 +75,6 @@ end
 module Landline
   module DSL
     module ProbeMethods
-      # TODO: If probe execution contexts are somehow shared between threads
-      # this could result in a session leakage through race condition.
-
       # (in Landline::Probe context)
       # Return session storage hash
       # @return [Landline::Session::Session]