Remove unused "prettier-config-standard" devDependency

[trivikr]

Is your feature request related to a problem? Please describe.

I was looking into dependencies, and noticed that prettier-config-standard is unused. https://github.com/search?q=repo%3Abluesky-social%2Fatproto%20prettier-config-standard&type=code

As per their docs, it needs to be added in prettier configuration file. And it's not listed there https://github.com/bluesky-social/atproto/blob/main/.prettierrc

While looking into history, I noticed it was added in https://github.com/bluesky-social/atproto/pull/152, but was never used. It appears safe to remove it.

Describe the solution you'd like

Remove unused "prettier-config-standard" devDependency