bump: rust 1.73 #1833

Job	Run time
Check	3m 41s
Test C++ Runtime (ubuntu-latest)	6m 4s
Doctest Rust (ubuntu-latest)	4m 28s
Check Style	3m 20s
Test C++ Runtime (windows-latest)	5m 12s
Doctest Rust (windows-latest)	2m 44s
Test Rust (ubuntu-latest)	7m 17s
Test C++ Runtime (macOS-latest)	7m 58s
Doctest Rust (macOS-latest)	2m 3s
Test Rust (windows-latest)	11m 43s
Test mdbook	2m 31s
Test Rust (macOS-latest)	6m 32s
	1h 3m 33s

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