Fix NilClass compatibility shim: add missing taint and untaint methods

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: GarthDB

_plugins/ruby33_compat.rb

@@ -19,6 +19,14 @@ class NilClass
     def tainted?
       false
     end
+
+    def taint
+      self
+    end
+
+    def untaint
+      self
+    end
   end
 
   class Object