Feature tool_lints is not stabilized until 1.31

[jtgeibel]

The release notes currently state (last item under Misc) that the tool_lints feature is stabilized. It links to #53459 where some warnings were added directing users to the new syntax, but the feature wasn't actually stabilized until #54870 and is currently only available on nightly. I tested locally with both beta and the pre-release builds of 1.30.0.

[petrochenkov]

@jtgeibel
The release notes talk about tool attributes (#[rustfmt::skip]) rather than tool lints (#[allow(clippy::something)]).
Tool attributes were indeed stabilized on 1.30.
(Closing as not-an-issue.)