DEV: Skip compressing theme test files (PR #13619)

Doing this shaves off ~34 seconds on the rebuild time of a site in a self-hosted Digital Ocean droplet for me (5m31s vs 4m57s).

Since these files are only used by developers, I think it’s worth the tradeoff of uncompressed bundles in favor of saving on rebuild time.

GitHub

Sure, I think this makes sense. Let’s give it a try!