protocols/kad/src/kbuckets: Explicitly convert u8 to usize

[mxinden]

Compiling libp2p-kad for --target wasm32-unknown-unknown fails with
the cryptic error message cannot infer type for type usize.
Explicitly converting to usize solves the issue.

961error[E0283]: type annotations needed
962   --> /usr/local/cargo/registry/src/github.com-1ecc6299db9ec823/libp2p-kad-0.22.0/src/kbucket.rs:123:19
963    |
964123 |         if self.0 == u8::MAX.into() {
965    |                   ^^ cannot infer type for type `usize`
966    |
967    = note: cannot satisfy `usize: std::cmp::PartialEq<_>`

I am not familiar enough with wasm32-unknown-unknown to know the exact cause. In case you deem it to be worth the effort, I am happy to dig deeper into this.

Likely related to rust-lang/rust#71584 and rust-lang/rust#71538.

Needed for paritytech/substrate#6891.

[romanb]

👍 For quick patches like this that you want released, the most convenient way is to bump (patch) version and changelog here already and release just this crate on merge. If #1714 is merged before this PR, which contains changes for the next minor release, you may need to make the patch release on a release branch for the prior release and backport it to master.

[mxinden]

@romanb just to make sure we are on the same page: I will not release a patch version of the root level crate (libp2p) as this is not an urgent security fix. I will only release a patch version of libp2p-kad. Do you agree with that?

[romanb]

@romanb just to make sure we are on the same page: I will not release a patch version of the root level crate (libp2p) as this is not an urgent security fix. I will only release a patch version of libp2p-kad. Do you agree with that?

Yes.