Add option to suppress feedback messages

This is used to dynamically exclude some test results from being shown to users, but still allows them to run in the background (e.g., for research).

lib/python20_course_week.rb

@@ -1,24 +0,0 @@
-# frozen_string_literal: true
-
-class Python20CourseWeek
-  def self.get_for(exercise)
-    case exercise.title
-      when /Python20 Aufgabe 1/
-        1
-      when /Python20 Aufgabe 2/
-        2
-      when /Python20 Aufgabe 3/
-        3
-      when /Python20 Aufgabe 4/, /Python20 Snake/
-        4
-      # else: Not part of the Python20 course
-    end
-  end
-
-  def self.show_linter?(exercise)
-    week = get_for(exercise)
-    return true if week.nil? # Exercise is not part of the experiment
-
-    [3, 4].include?(week)
-  end
-end