Revert "test/lib/leakchecker.rb (find_tempfiles): don't warn for missing files"

This reverts commit 52102f6ff50eebf8c16667c9b49cef579d2057c1 (r64238).

It is no longer necessary if we use Tempfile.create in
WEBrick::HTTPAuth::Htgroup#flush (see next commit)

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64362 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/lib/leakchecker.rb

@@ -128,8 +128,7 @@ class LeakChecker
       [prev_count, []]
     else
       tempfiles = ObjectSpace.each_object(Tempfile).find_all {|t|
-        t.instance_variable_defined?(:@tmpfile) and t.path and
-          File.exist?(t.path)
+        t.instance_variable_defined?(:@tmpfile) and t.path
       }
       [count, tempfiles]
     end