upgrade docify to 0.2.5 (#2052)

Updates `docify` to 0.2.5, which fixes some indentation bugs and adds
the new `#[docify::export_content]` attribute which can be used like
regular `#[docify::export]` but will only export the _underlying
contents_ of the item it is attached to, if applicable (otherwise it
just behaves exactly like `#[docify::export]`).

Release notes here:
https://github.com/sam0x17/docify/releases/tag/v0.2.5

cc @Kianenigma