serdect: bump `toml` to v0.8 (#1244) #683

Job	Run time
build (1.65.0, thumbv7em-none-eabi)	5m 46s
test (1.65.0)	5m 8s
build (1.65.0, wasm32-unknown-unknown)	5m 34s
test (stable)	34s
build (stable, thumbv7em-none-eabi)	29s
build (stable, wasm32-unknown-unknown)	34s
minimal-versions / minimal-versions	1m 18s
	19m 23s

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