Changed secret.add example values to avoid further confusion (#1524)

* changed secret.add values to avoid further confusion

* Apply suggestions from code review

---------

Co-authored-by: Angelika Cathor <angelikatyborska@fastmail.com>

exercises/concept/secrets/.docs/instructions.md

@@ -11,9 +11,9 @@ All functions should expect integer arguments. Integers are also suitable for pe
 Implement `Secrets.secret_add/1`. It should return a function which takes one argument and adds to it the argument passed in to `secret_add`.
 
 ```elixir
-adder = Secrets.secret_add(2)
+adder = Secrets.secret_add(3)
 adder.(2)
-# => 4
+# => 5
 ```
 
 ## 2. Create a subtractor

exercises/concept/secrets/test/secrets_test.exs

@@ -3,9 +3,9 @@ defmodule SecretsTest do
 
   describe "secret_add" do
     @tag task_id: 1
-    test "add 3" do
-      add = Secrets.secret_add(3)
-      assert add.(3) === 6
+    test "add 4" do
+      add = Secrets.secret_add(4)
+      assert add.(3) === 7
     end
 
     @tag task_id: 1