Remove conflicting advice

[BenjaminBrienen]

The advice in the style guide conflicts with a clippy lint.
Also, the "bad" style is consistently used throughout the repository, especially when comparing an index to a length.

warning: this boolean expression can be simplified
   --> crates/hir-def/src/expr_store/lower/asm.rs:244:44
    |
244 | ...                   if !(idx < operands.len())
    |                          ^^^^^^^^^^^^^^^^^^^^^^^ help: try: `(idx >= operands.len())`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#nonminimal_bool
    = note: `-W clippy::nonminimal-bool` implied by `-W clippy::complexity`
    = help: to override `-W clippy::complexity` add `#[allow(clippy::nonminimal_bool)]`

[fee1-dead]

I'm not sure if this is an improvement, because clippy lints are meant to be annoying (cause, clippy) lints that you can choose to follow or ignore.

But it's probably clearer to cite specific instances of both styles used in this repository so we can get a better picture?

[BenjaminBrienen]

The "suggested" style is simply not used in the repo except in some obscure test data.

edit: !\(.* [<>+=]+ .*\) yields 12 actual code results, of which, only a few are "true" matches

[BenjaminBrienen]

\b[a-z_.()0-9]* (<=|>=)+ \S*\b yields 236 results that seem like relevant examples at a glance