Update proc-macro-crate requirement in /proc-macro-definitions #858

Job	Run time
Book	54s
Browser Test	1m 24s
Check on Rust 1.58 (macos)	13s
Check on Rust stable (macos)	7s
Minimal Versions	42s
Miri	27s
Check on Rust beta (macos)	14s
Test	20s
Check on Rust nightly (macos)	13s
Check on Rust 1.58 (ubuntu)	14s
Check on Rust stable (ubuntu)	9s
Check on Rust beta (ubuntu)	12s
Check on Rust nightly (ubuntu)	12s
Check on Rust 1.58 (windows)	9s
Check on Rust stable (windows)	13s
Check on Rust beta (windows)	15s
Check on Rust nightly (windows)	11s
	6m 9s

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