* drop empty lines when diffing output
* replace expected css with optimized lightningcss output
Lightning CSS generates a more optimal CSS output.
Right now the tests are setup in a way that both the generated css and
expected css are run through `lightningcss` to make sure that the output
is concistent for the `stable` and `oxide` engines. But this also means
that the expected output _could_ be larger (aka not optimized) and still
matches (after it runs through lightningcss).
By replacing this with the more optimal output we achieve a few things:
1. This better reflects reality since we will be using `lightningcss`.
2. This gets rid of unnecessary css.
3. Removed code!
