Auto merge of #56565 - matthiaskrgr:clippy, r=oli-obk

submodules: update clippy from 29bf75c to 1df5766

Fixes clippy toolstate.

Changes:
````
Remove -preview suffix from README
rustup clippy build with latest rustc (breakage due to 08f8fae )
Forgot to remove some debugging code ...
Improved code noted by clippy.
Fix bug in `implicit_return`. Bug was already covered by test, but test was not checked for.
fix #3482 and add ui test for it
Don't change current working directory of cargo tests
Use cargo's "PROFILE" envvar and set CLIPPY_DOGFOOD
Use dogfood_runner for deterministic test ordering
Remove unnecessary documentation
Fix dogfood tests.
Added additional reasoning to `Why is this bad?`. Added comment to explain usage of MIR.
Renamed to `implicit_return`. Covered all other kinds besides `ExprKind::Lit`. Added check for replacing `break` with `return`.
Appeasing the Test Gods. Seems I'm not smart enough to run the tests locally before committing.
Renamed `forced_return` to `missing_returns`. Better clarification in the docs. Ran `update_lints`.
Added `FORCED_RETURN` lint.
````
r? @oli-obk

Author: bors