test_parse.rb: fix variable name

* test/ruby/test_parse.rb (test_dstr_disallowed_variable): fix
  duplicate variable name to be tested.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@50478 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_parse.rb

@@ -362,7 +362,7 @@ class TestParse < Test::Unit::TestCase
 
   def test_dstr_disallowed_variable
     bug8375 = '[ruby-core:54885] [Bug #8375]'
-    %w[@ @1 @@. @@ @@1 @@. $ $%].each do |src|
+    %w[@ @1 @. @@ @@1 @@. $ $%].each do |src|
       src = '#'+src+' '
       str = assert_nothing_raised(SyntaxError, "#{bug8375} #{src.dump}") do
         break eval('"'+src+'"')