CI: fail on warnings in `features-check` #2307

Job	Run time
check-docs	41s
cross-targets (x86_64-sun-solaris)	1m 55s
alternative_targets (ubuntu-latest, wasm32-wasi)	10s
alternative_targets (ubuntu-latest, wasm32-unknown-emscripten)	23s
alternative_targets (ubuntu-latest, aarch64-apple-ios)	16s
alternative_targets (ubuntu-latest, aarch64-linux-android)	20s
no_std (ubuntu-latest, thumbv6m-none-eabi)	16s
no_std (ubuntu-latest, x86_64-fortanix-unknown-sgx)	18s
rust_msrv (ubuntu-latest)	4m 42s
features_check (ubuntu-latest)	7m 38s
features_check (macos-latest)	14m 56s
features_check (windows-latest)	16m 6s
rust_versions (ubuntu-latest, stable)	1m 34s
rust_versions (ubuntu-latest, beta)	1m 51s
rust_versions (ubuntu-latest, nightly)	1m 56s
timezones_linux (ubuntu-latest, ACST-9:30)	2m 19s
timezones_linux (ubuntu-latest, EST4)	2m 20s
timezones_linux (ubuntu-latest, UTC0)	2m 11s
timezones_linux (ubuntu-latest, Asia/Katmandu)	2m 40s
test_wasm (ubuntu-latest)	24s
timezones_other (macos-latest, ACST-9:30)	1m 23s
timezones_other (macos-latest, EST4)	1m 23s
timezones_other (macos-latest, UTC0)	1m 33s
timezones_other (macos-latest, Asia/Katmandu)	1m 26s
timezones_other (windows-latest, ACST-9:30)	2m 32s
timezones_other (windows-latest, EST4)	5m 19s
timezones_other (windows-latest, UTC0)	3m 7s
timezones_other (windows-latest, Asia/Katmandu)	3m 10s
	1h 22m 49s

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