Fix test import warning

When running `$ grunt` and using Sass 3.2.6 I was receiving this warning:

```
Running "sass:compile" (sass) task
WARNING: On line 1:
  It's not clear which file to import for '@import "imported"'.
  Candidates:
    imported.sass
    imported.scss
  For now I'll choose imported.sass.
  This will be an error in future versions of Sass.

WARNING: On line 1:
  It's not clear which file to import for '@import "imported"'.
  Candidates:
    imported.sass
    imported.scss
  For now I'll choose imported.sass.
  This will be an error in future versions of Sass.
```

This pull request updates the two compile fixtures to remove that warning.