Gutenboarding: Remove stray style import

[ockham]

Changes proposed in this Pull Request

Leftover from #38282. Obsolete as of #38456.

Testing instructions

Verify that Gutenboarding still works.

[matticbot]

Test live: https://calypso.live/?branch=remove/gutenboarding-stray-style-import

[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

App Entrypoints (~120 bytes removed 📉 [gzipped])

name                 parsed_size           gzip_size
entry-gutenboarding       -295 B  (-0.0%)     -120 B  (-0.0%)

Common code that is always downloaded and parsed every time the app is loaded, no matter which route is used.

Legend

What is parsed and gzip size?

Parsed Size: Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory.
Gzip Size: Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.

[sirreal]

Thanks!