Stop linting assert!(x == y)

[thelearnerofcode]

fixes #2090

[clarfonthey]

I think that instead of removing the lint entirely, it should just be switched to allow by default. Additionally, the inverse of the lint should probably be added, linting changing assert_eq! to assert!

[oli-obk]

Why should we keep this lint? Can you elaborate on that?

We should not add the inverse lint until the RFC is implemented.

[Manishearth]

I think that instead of removing the lint entirely, it should just be switched to allow by default.

We already have a mechanism for deprecating lints; we can just use that. This makes the lint do nothing and warn on being used, but won't suddenly break code that has #[allow(name_of_lint)] because the lint is suddenly unknown.

On that note, this PR does not do that, it should.

[oli-obk]

@thelearnerofcode friendly ping

You need to

1. rebase
2. add the removed lint to the list of deprecated lints

[oli-obk]

Has been fixed in another PR.