Bump dtolnay/rust-toolchain from 1.63.0 to 1.64.0 #330

Job	Run time
Test Suite (ubuntu-latest, stable)	4m 39s
Test Suite (ubuntu-latest, nightly)	5m 37s
Clippy	2m 13s
Check	51s
Rustfmt	9s
Test Suite (macos-latest, stable)	4m 52s
Test Suite (macos-latest, nightly)	4m 43s
MSRV	4m 28s
Test Suite (windows-latest, stable)	11m 14s
spellcheck	12s
Test Suite (windows-latest, nightly)	8m 53s
	47m 51s

Provide feedback