submodules: update clippy from 3710ec5 to ad3269c

Changes:
````
Rustfmt all the things
Clippy dogfood
Update for compiletest changes
Use symbols instead of strings
Rustup to rustc 1.36.0-nightly (1764b29 2019-05-12)
Add regression test for identity_conversion FP
UI test cleanup: Extract many_single_char_names tests
Add tests for empty_loop lint
Add in_macro again
Rename in_macro to in_macro_or_desugar
````