Clarify `receive_onchain` docs #3803

Job	Run time
Test sdk-common	36s
Test sdk-core	1m 26s
Test sdk-cli	1m 8s
Test sdk-bindings	2m 55s
Clippy	1m 5s
Check flutter	2m 49s
Format	8s
Check SDK as Rust dependency in fresh project	2m 46s
Check react native	1m 24s
	14m 17s

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