…frewsxcv

Fix Markdown list formatting.

The Markdown engine used by the book can cope with a single leading space on the list marker:

    Like this:

     * List item

    Rather than like this:

    * List item

… but it’s not the typical convention employed in the book, and moreover the Markdown engine used for producing the error index *can’t* cope with it (its behaviour looks like a bug, as it appears to lose one of the two line breaks as well, but that’s immaterial here).

So, we shift to a single convention which doesn’t trigger bugs in the Markdown renderer.

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See https://doc.rust-lang.org/error-index.html#E0458 and https://doc.rust-lang.org/error-index.html#E0101 for the bad current rendering in the error index.

Rollup of 14 pull requests

- Successful merges: #37956, #38013, #38297, #38480, #38497, #38502, #38505, #38513, #38521, #38549, #38554, #38557, #38568, #38572
- Failed merges: