Add rustless.org to documentation blocklist

[XAMPPRocky]

Found on: https://crates.io/crates/valico

No longer hosts any kind of rust documentation.

r? @carols10cents

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @carols10cents (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

[JustAPerson]

Also need to update the cargo reference

[XAMPPRocky]

@JustAPerson I've now created a second PR doing that.

[pietroalbini]

Added this to the crates.io team meeting agenda.

[carols10cents]

We discussed this in the meeting and agreed on it but I forgot to approve this, oops.

@bors r+

[bors]

📌 Commit 2fd9289 has been approved by carols10cents

[bors]

⌛ Testing commit 2fd9289 with merge 974b664...

[bors]

☀️ Test successful - checks-travis
Approved by: carols10cents
Pushing 974b664 to master...