Bump proc-macro-crate from 2.0.1 to 3.0.0 (#558) #32

Job	Run time
set-image	1s
tests	2m 57s
clippy	1m 39s
checks	1m 31s
bench-rust-nightly (bit-vec)	17m 57s
miri (bit-vec)	49m 23s
miri (bytes)	2m 53s
bench-rust-nightly (bytes)	17m 5s
miri (generic-array)	2m 55s
bench-rust-nightly (generic-array)	17m 2s
miri (arbitrary)	2m 52s
bench-rust-nightly (derive)	17m 0s
bench-rust-nightly (max-encoded-len)	17m 1s
build-linux-ubuntu-amd64	1m 21s
publish-dry-run	1m 14s
	2h 32m 51s

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