Update proc-macro-crate requirement in /proc-macro-definitions #864

Job	Run time
Miri	26s
Browser Test	1m 20s
Book	44s
Minimal Versions	35s
Check on Rust 1.58 (macos)	12s
Test	6s
Check on Rust stable (macos)	11s
Check on Rust beta (macos)	11s
Check on Rust nightly (macos)	10s
Check on Rust 1.58 (ubuntu)	9s
Check on Rust stable (ubuntu)	3s
Check on Rust beta (ubuntu)	9s
Check on Rust nightly (ubuntu)	8s
Check on Rust 1.58 (windows)	3s
Check on Rust stable (windows)	2s
Check on Rust beta (windows)	7s
Check on Rust nightly (windows)	2s
	4m 38s

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