Auto merge of #13261 - antonilol:fix-doc-code-blocks, r=xFrednet

fix code blocks in doc comments inconsistently using 3 or 4 spaces of indentation

The metadata collector script was treating the space lines all start with as indentation. This caused code block's triple backticks to get a space in front of it, like this:
```
 ```rust
^ this space
```
Code after that that is indented with 4 spaces will only have 3 of those rendered.
Example (taken from [here](https://rust-lang.github.io/rust-clippy/master/index.html#/missing_panics_doc)):
```rust
...
pub fn divide_by(x: i32, y: i32) -> i32 {
   if y == 0 {                      // 3 spaces
       panic!("Cannot divide by 0") // 7 spaces
...
```

Also added 'compile_fail' alongside the other rustdoc directives (second code block [here](https://rust-lang.github.io/rust-clippy/master/index.html#/macro_metavars_in_unsafe) had no highlighting), fixed a doc comment using 'rs' instead of 'rust' and removed some spaces causing an extra missing space of indentation (see second code block [here](https://rust-lang.github.io/rust-clippy/master/index.html#/map_err_ignore)).

changelog: none

0 files changed, 0 insertions, 0 deletions