Rollup merge of rust-lang#83206 - ehuss:update-books, r=ehuss

Update books

## nomicon

1 commits in adca786547d08fe676b2fc7a6f08c2ed5280ca38..6fe476943afd53a9a6e91f38a6ea7bb48811d8ff
2021-02-16 16:34:20 +0900 to 2021-03-10 07:28:57 +0900
- Merge pull request rust-lang/nomicon#257 from skade/opaque-types-fix

## reference

3 commits in 3b6fe80c205d2a2b5dc8a276192bbce9eeb9e9cf..e32a2f928f8b78d534bca2b9e7736413314dc556
2021-02-22 22:09:17 -0800 to 2021-03-08 23:24:30 -0800
- Clarify that ::foo paths are not necessarily based off of the "crate root" (rust-lang/reference#974)
- Comment typo (rust-lang/reference#977)
- Fix misspelled word discrimnant (rust-lang/reference#976)

## book

2 commits in 0f87daf683ae3de3cb725faecb11b7e7e89f0e5a..fc2f690fc16592abbead2360cfc0a42f5df78052
2021-03-01 08:54:04 -0500 to 2021-03-05 14:03:22 -0500
- Fix wrapping
- fix: redundant double introduction of shadowing (rust-lang/book#2633)

## rust-by-example

1 commits in 3e0d98790c9126517fa1c604dc3678f396e92a27..eead22c6c030fa4f3a167d1798658c341199e2ae
2021-02-25 08:23:10 -0300 to 2021-03-04 16:26:43 -0300
- Fix grammar "terminates" -> "terminate" (rust-lang/rust-by-example#1423)

## rustc-dev-guide

15 commits in c431f8c..67ebd4b
2021-02-28 16:35:20 -0500 to 2021-03-11 13:36:25 -0800
- Remove extra the (rust-lang/rustc-dev-guide#1088)
- Fix double-word typos (rust-lang/rustc-dev-guide#1084)
- I-nominated are nominated for discussion (rust-lang/rustc-dev-guide#1080)
- Complete unfinished statement
- Check `BASE_SHA` only if it's a PR (rust-lang/rustc-dev-guide#1083)
- Update lins
- Apply suggestions from code review
- Add stub about the THIR
- Switch from Travis to GHA (rust-lang/rustc-dev-guide#1073)
- Adjust a bit better P- label text
- Fix typos (rust-lang/rustc-dev-guide#1079)
- Update cmake version in prerequisites.md (rust-lang/rustc-dev-guide#1077)
- Fix typo: suceed -> succeed
- Add article on using WPA to profile rustc memory usage on Windows (rust-lang/rustc-dev-guide#1074)
- Use more accurate estimate of generated LLVM IR with llvm-lines

## embedded-book

1 commits in a96d096cffe5fa2c84af1b4b61e1492f839bb2e1..f61685755fad7d3b88b4645adfbf461d500563a2
2021-02-17 08:08:52 +0000 to 2021-03-08 01:06:44 +0000
- Swap to GHA  (rust-embedded/book#285)