serdect: bump `toml` to v0.8 (#1244) #892

Job	Run time
test (1.65.0)	6m 17s
build (1.65.0, thumbv7em-none-eabi)	4m 45s
test (stable)	47s
build (1.65.0, wasm32-unknown-unknown)	4m 38s
build (stable, thumbv7em-none-eabi)	15s
build (stable, wasm32-unknown-unknown)	15s
minimal-versions / minimal-versions	1m 32s
	18m 29s

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