docs: fix MD024/no-duplicate-heading lint issue

[alexandear]

Fixes #1506

[chavacava]

(It's a shame that we will need to repeat the section title in the subsection to avoid name clashes. It neutralizes all the interest of organizing information in nested structures.)

[ccoVeille]

Yes, and no.

The rule can be disabled. But then it means direct link to this section are not stable.

Disabling the rule for a changelog is logic, here it's a bit different

[alexandear]

(It's a shame that we will need to repeat the section title in the subsection to avoid name clashes. It neutralizes all the interest of organizing information in nested structures.)

Repeating the section title has an advantage: we can have a direct link to a rule example on the website, e.g. https://revive.run/r#examples-bool-literal-in-expr (will be available after the next release).