Bump `serdect` dependency to v0.3 (#719) #1933

Job	Run time
careful	1m 36s
build-benchmarks	38s
build (1.83.0, thumbv7em-none-eabi)	44s
build (1.83.0, wasm32-unknown-unknown)	40s
cross (aarch64-unknown-linux-gnu, stable)	3m 39s
clippy	21s
build (stable, thumbv7em-none-eabi)	37s
cross (powerpc-unknown-linux-gnu, stable)	5m 30s
doc	23s
build (stable, wasm32-unknown-unknown)	37s
minimal-versions	22s
miri (x86_64-unknown-linux-gnu)	3m 58s
rustfmt	5s
miri (s390x-unknown-linux-gnu)	4m 12s
test (i686-unknown-linux-gnu, 1.83.0, sudo apt update && sudo apt install gcc-multilib)	2m 28s
test (i686-unknown-linux-gnu, stable, sudo apt update && sudo apt install gcc-multilib)	2m 22s
test (x86_64-unknown-linux-gnu, 1.83.0)	1m 47s
test (x86_64-unknown-linux-gnu, stable)	1m 45s
	31m 44s

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