Remove rustc-dev component from default profile

[jethrogb]

The rustc-dev component is larger than all other components of the default profile combined, yet most users probably don't care about this. I think it should be removed.

Perhaps another profile default-poweruser can be made that does include it.

[kinnison]

I'd argue that the complete profile (which is basically rust devs-only anyway) might be an acceptable place for this, without needing to add a new profile name. People who want default plus rustc-dev can just do rustup toolchain install nightly --profile default --component rustc-dev

[Mark-Simulacrum]

It was the intent when merging the PR that split the rustc-dev profile out that we would eventually remove it from the default set. I believe this is already true on beta (and perhaps stable as of later today?).

I would accept a PR at this point that removes rustc-dev component from the default set on nightly as well.