Uncommented setting of bundle response files back.

When those lines were commented, less bundle worked incorrectly when optimizations are turned on.
In my project I have _main.less_ file:
```less
@import "main-variables.less";
// styles
```
_main-variables.less_:
```less
@foobar: 20px;
// other variables
```
and my _BundleConfig.cs_:
```c#
bundles.Add(new LessBundle("~/bundles/css").Include("~/Content/pages/main/main.less"));
```
With original version of the code (where lines are commented) output of _main.less_ never changes if I change variables from _main-variables.less_ (bundle optimizations shall be turned on).
With my changes this problem disappears.