sec1: bump `serdect` dependency to v0.3.0-rc.0 (#1523) #1286

Job	Run time
build (1.75.0, thumbv7em-none-eabi)	28s
test (1.75.0)	38s
build (1.75.0, wasm32-unknown-unknown)	33s
build (stable, thumbv7em-none-eabi)	22s
test (stable)	30s
build (stable, wasm32-unknown-unknown)	26s
minimal-versions	0s
	2m 57s

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