fix: hugr-py not adding extension-reqs on custom ops (#1759) #2877

Job	Run time
Check for changes	5s
tests (Rust nightly, coverage)	4m 30s
check	1m 13s
Build benchmarks 🏋️	2m 25s
tests (Rust 1.75)	2m 28s
tests (Rust stable, all features)	2m 24s
tests (Rust beta)	2m 34s
tests hugr-llvm (14.0, 14-0)	1m 50s
tests (Rust stable, no features)	1m 26s
Check standard extensions	7s
Required checks 🦀	1s
	19m 3s

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