Fix references to String.capitalize/1

Author: josevalim

lib/ex_unit/lib/ex_unit/case.ex

@@ -418,13 +418,13 @@ defmodule ExUnit.Case do
       defmodule StringTest do
         use ExUnit.Case, async: true
 
-        describe "String.capitalize/1" do
-          test "first grapheme is in uppercase" do
-            assert String.capitalize("hello") == "Hello"
+        describe "String.downcase/1" do
+          test "with ascii characters" do
+            assert String.downcase("HELLO") == "hello"
           end
 
-          test "converts remaining graphemes to lowercase" do
-            assert String.capitalize("HELLO") == "Hello"
+          test "with Unicode" do
+            assert String.downcase("HÉLLÒ") == "héllò"
           end
         end
       end