fix: bad indent in doc comments (#14419)

TLDR
```diff
- ///    01234
+ ///     01234
     12345
```

Sometimes, in doc comments, there are 3 spaces + 1 instead of 4 spaces +
1.
To make it coherent with the rest of the clippy codebase, I `fd -t f -X
sed -E -i 's,///\s{4}(\S),/// \1,g'` and manually verified and fixed the
relevant part of code that had bad indentation.

### Example

```rs
/// fn a() {
///    01234
/// }
```
Becomes
```rs
/// fn a() {
///     01234
/// }
```

changelog: none

0 files changed, 0 insertions, 0 deletions