Fix unknown doc attribute Hidden at nightly

[zzau13]

The Hidden doc attribute it's no longer valid at nightly

[Robbepop]

Also breaks my build. :(

   Compiling tinytemplate v1.2.0
error: unknown `doc` attribute `Hidden`
  --> /home/me/.cargo/registry/src/github.com-1ecc6299db9ec823/tinytemplate-1.2.0/src/error.rs:44:11
   |
44 |     #[doc(Hidden)]
   |           ^^^^^^

[zzau13]

But that's what I'm fixing. Is there a problem with the cache on the CI?

[paolobarbolini]

Is there a problem with the cache on the CI?

criterion is being used as a dev-dependency, and it's importing this crate from crates.io.

[zzau13]

Ok, there is a cyclic dependency.

But this is a criterion bug nightly so it should be fixed from the criterion repository. From here I can't do anything. Remove dependency, little more.

It's just in the benchmarks I don't think it's important.

[Manishearth]

To be clear this is a rustc regression (rust-lang/rust#82662), and we hope to fix it in the next nightly (rust-lang/rust#82702), but until then it would be really great if this could be landed with a version bump

[bheisler]

Thanks for the pull request!