Rollup merge of #155568 - rustbot:docs-update, r=ehuss

Update books

## rust-embedded/book

2 commits in 2463edeb8003c5743918b3739a9f6870b86396f5..0789b0f29e73ecb91213cac10ad0eec1b9333770
2026-04-11 08:46:22 UTC to 2026-04-10 14:01:38 UTC

- remove IO chapter, is covered in next chapter (rust-embedded/book#411)
- add embassy chapter (rust-embedded/book#412)

## rust-lang/reference

10 commits in d2715c07e9dd9839c0c7675ecfa18bec539a6ee9..8c88f9d0bdd75ffdc0691676d83212ae22a18cee
2026-04-20 15:20:24 UTC to 2026-04-07 16:25:09 UTC

- typo in example code (rust-lang/reference#2232)
- oxford comma (rust-lang/reference#2233)
- improve readability (rust-lang/reference#2234)
- typo (rust-lang/reference#2230)
- Clarify items.fn.generics.param-bounds (rust-lang/reference#2229)
- follow formatting style guideline (rust-lang/reference#2228)
- Update `derive` export locations (rust-lang/reference#2223)
- Clarify that `{self}` imports require a module parent (rust-lang/reference#2221)
- stabilize s390x vector registers (rust-lang/reference#2215)
- Fix misuse of *usage* throughout the Reference (rust-lang/reference#2222)

## rust-lang/rust-by-example

2 commits in b31e3b8da01eeba0460f86a52a55af82709fadf5..898f0ac1479223d332309e0fce88d44b39927d28
2026-04-19 11:40:28 UTC to 2026-04-19 11:38:45 UTC

- remove debug printing for the u32 and bool in variable_bindings.md (rust-lang/rust-by-example#1999)
- Update for.md (rust-lang/rust-by-example#2008)

Author: jhpratt