Simple cipher remove test: do not check what happens with invalid input (#852)

Author: jiegillet

exercises/practice/simple-cipher/test/simple_cipher_test.exs

@@ -72,12 +72,6 @@ defmodule SimpleCipherTest do
     assert SimpleCipher.decode("zabcdefghi", "abcdefghij") == "zzzzzzzzzz"
   end
 
-  @tag :pending
-  test "only lowercase a-z are translated, rest are passed through" do
-    assert SimpleCipher.encode("this is a test!", "d") == "wklv lv d whvw!"
-    assert SimpleCipher.decode("wklv lv d whvw!", "d") == "this is a test!"
-  end
-
   @tag :pending
   test "can encode messages longer than the key" do
     assert SimpleCipher.encode("abc", "a") == "abc"