der_derive: fix doc typo and use a valid tag number #2370

Job	Run time
build (1.65.0, thumbv7em-none-eabi)	4m 51s
build (1.65.0, wasm32-unknown-unknown)	4m 11s
build (stable, thumbv7em-none-eabi)	2m 47s
build (stable, wasm32-unknown-unknown)	2m 9s
derive (1.65.0)	1m 42s
derive (stable)	33s
test (i686-unknown-linux-gnu, ubuntu-latest, 1.65.0, sudo apt update && sudo apt install gcc-mult...	21m 22s
test (i686-unknown-linux-gnu, ubuntu-latest, stable, sudo apt update && sudo apt install gcc-mult...	18m 2s
test (x86_64-unknown-linux-gnu, ubuntu-latest, 1.65.0)	25m 49s
test (x86_64-unknown-linux-gnu, ubuntu-latest, stable)	17m 58s
minimal-versions / minimal-versions	14m 34s
	1h 53m 58s

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