[hello-world] update to current version of canonical data

This is in line with exercism/problem-specifications#544

exercises/hello-world/src/example.erl

@@ -1,8 +1,8 @@
 -module(example).
--export([greet/0, greet/1, test_version/0]).
+-export([hello/0, test_version/0]).
 
-greet() -> "Hello, World!".
-greet(Name) -> "Hello, " ++ Name ++ "!".
+hello() ->
+  "Hello, World!".
 
 test_version() ->
-    1.
+  2.

exercises/hello-world/test/hello_world_tests.erl

@@ -1,18 +1,9 @@
 -module(hello_world_tests).
 
 -define(TESTED_MODULE, (sut(hello_world))).
--define(TEST_VERSION, 1).
+-define(TEST_VERSION, 2).
 -include("exercism.hrl").
 
 
-no_name_test() ->
-  ?assertEqual("Hello, World!", ?TESTED_MODULE:greet()).
-
-alice_test() ->
-  ?assertEqual("Hello, Alice!", ?TESTED_MODULE:greet("Alice")).
-
-bob_test() ->
-  ?assertEqual("Hello, Bob!", ?TESTED_MODULE:greet("Bob")).
-
-strange_test() ->
-  ?assertEqual("Hello, !", ?TESTED_MODULE:greet("")).
+say_hi_test() ->
+  ?assertEqual("Hello, World!", ?TESTED_MODULE:hello()).