[FIX] Remove warning: literal string will be frozen in the future from render_test

Author: maniSHarma7575

actionview/test/template/render_test.rb

@@ -793,7 +793,7 @@ def test_render_object
   end
 
   def test_render_mutate_string_literal
-    assert_equal "foobar", @view.render(inline: "'foo' << 'bar'", type: :ruby)
+    assert_equal "foobar", @view.render(inline: "+'foo' << 'bar'", type: :ruby)
   end
 end