Use stable Rust for checks

Using the nightly compiler is a burden for contributors — a lot of
platforms don't ship a builds of the nightly compiler. In order to use
nightly, we'd need to compile it from source.

Author: WhyNotHugo

Makefile

@@ -2,16 +2,18 @@ test:
 	@cargo test --all-features --all-targets
 
 check:
-	@cargo +nightly fmt --all
+	@cargo fmt --all
 	@cargo clippy --fix --allow-dirty --allow-staged --all-targets --all-features
 	@cargo update --dry-run
 	@cargo outdated -wR
 	@cargo machete
 	@cargo doc --no-deps --all-features --examples --document-private-items
-	@cargo +nightly udeps --all-targets --all-features
+	@cargo udeps --all-targets --all-features
 
 check_nightly:
+	@cargo +nightly fmt --all
 	@cargo +nightly clippy --fix --allow-dirty --allow-staged --all-targets --all-features
+	@cargo +nightly udeps --all-targets --all-features
 
 check_strictly:
 	@cargo +nightly clippy --fix --allow-dirty --allow-staged --all-features --all-targets -- -W clippy::all -W clippy::pedantic -W clippy::cargo