test_win32api.rb: suppress a warning

* test/test_win32api.rb: suppress a warning, which we know already
  well.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64816 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/test_win32api.rb

@@ -1,8 +1,11 @@
 # frozen_string_literal: false
 require "test/unit"
 begin
+  $VERBOSE, verbose = nil, $VERBOSE
   require "Win32API"
 rescue LoadError
+ensure
+  $VERBOSE = verbose
 end
 
 class TestWin32API < Test::Unit::TestCase