fix(rust): make rust doc tests not run with nightly #2616

Job	Run time
ci / discover	15s
ci / check / .+check-bash	39s
ci / check / .+check-markdown	33s
ci / check / .+check-spelling	37s
ci / check / ./examples/go+check	28s
ci / check / ./examples/postgresql+check	29s
ci / check / ./examples/python+check	30s
ci / check / ./examples/rust+check	48s
ci / check / ./utilities/cql-to-d2+check	36s
ci / check / ./utilities/earthly-cache-watcher+check	30s
ci / check / ./utilities/fetcher+check	29s
ci / check / ./utilities/jorm-metrics-server+check	26s
ci / build / ./examples/go+build	28s
ci / build / ./examples/postgresql+build	3m 0s
ci / build / ./examples/rust+build	58s
ci / build / ./examples/wasm/c+build	31s
ci / build / ./utilities/fetcher+build	27s
ci / build / ./utilities/jorm-metrics-server+build	28s
ci / package	0s
ci / test	0s
ci / release	0s
ci / docs	0s
ci / deploy	0s
ci / final	0s
	12m 12s

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