Rustdoc should give an error if you set both `doc(inline)` and `doc(no_inline)`

[jyn514]

Given the following code:

#![crate_type = "lib"]

pub mod inner {
    pub struct S;
}

#[doc(inline)]
#[doc(no_inline)]
pub use inner::S;

Rustdoc will generate
This is bogus: rustdoc is ignoring one of the attributes. Instead, it should give an error that you can't apply both attributes to the same item.

Thought of while reviewing #80267.

[LeSeulArtichaut]

I'll take a look at this as a first rustdoc issue :)