[Tests] Assert Module#set_temporary_name returns self

The return value of Module#set_temporary_name was changed
to return `self`, but the existing tests
did not verify this.

Author: aguspe

test/ruby/test_module.rb

@@ -3367,26 +3367,26 @@ def test_set_temporary_name
     m.const_set(:N, Module.new)
 
     assert_match(/\A#<Module:0x\h+>::N\z/, m::N.name)
-    m::N.set_temporary_name(name = "fake_name_under_M")
+    assert_same m::N, m::N.set_temporary_name(name = "fake_name_under_M")
     name.upcase!
     assert_equal("fake_name_under_M", m::N.name)
     assert_raise(FrozenError) {m::N.name.upcase!}
-    m::N.set_temporary_name(nil)
+    assert_same m::N, m::N.set_temporary_name(nil)
     assert_nil(m::N.name)
 
     m::N.const_set(:O, Module.new)
     m.const_set(:Recursive, m)
     m::N.const_set(:Recursive, m)
     m.const_set(:A, 42)
 
-    m.set_temporary_name(name = "fake_name")
+    assert_same m, m.set_temporary_name(name = "fake_name")
     name.upcase!
     assert_equal("fake_name", m.name)
     assert_raise(FrozenError) {m.name.upcase!}
     assert_equal("fake_name::N", m::N.name)
     assert_equal("fake_name::N::O", m::N::O.name)
 
-    m.set_temporary_name(nil)
+    assert_same m, m.set_temporary_name(nil)
     assert_nil m.name
     assert_nil m::N.name
     assert_nil m::N::O.name

variable.c

@@ -279,7 +279,7 @@ set_sub_temporary_name(VALUE mod, VALUE name)
  *    m.name #=> nil
  *
  *    c = Class.new
- *    c.set_temporary_name("MyClass(with description)")
+ *    c.set_temporary_name("MyClass(with description)") # => MyClass(with description)
  *
  *    c.new # => #<MyClass(with description):0x0....>
  *