Update rustls-platform-verifier requirement from 0.3 to 0.4 #551

Job	Run time
Clippy	53s
features	1m 33s
Check for documentation errors	19s
Build+test (stable, ubuntu-latest)	3m 0s
Format	11s
msrv	55s
Build+test (beta, ubuntu-latest)	3m 12s
Check semver compatibility	55s
Build+test (nightly, ubuntu-latest)	2m 39s
Build+test (macos-latest, stable)	2m 43s
Build+test (windows-latest, stable)	5m 34s
	21m 54s

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