chore: Remove default_members from Cargo.toml (#3006)

This PR removes the `default_members` from the workspace configuration. 

## Why

I'm not familiar with the motivation for why the `default_members` setting was added initially, and I do not object to keeping it. I'll explain my motivation for removing it below. 

My main reason for removing the `default_members` override is that new contributors may not know that `cargo test`, `cargo build`, and other commands only run on a subset of crates. They may then be surprised that their PRs are failing in CI, but everything works locally. 

My guess why `default_members` was added is to speed up the development workflow. That's fair, but I question the value because `ruff` is the heaviest crate to build.

Cargo.toml

@@ -1,6 +1,5 @@
 [workspace]
 members = ["crates/*"]
-default-members = ["crates/ruff", "crates/ruff_cli"]
 
 [workspace.dependencies]
 anyhow = { version = "1.0.66" }