chore: remove rlp encoding for `Request` #2374

Job	Run time
doctest	1m 42s
test ubuntu-latest stable --no-default-features	1m 31s
cfg-check	1m 20s
test ubuntu-latest stable	1m 45s
clippy	48s
test ubuntu-latest nightly --no-default-features	2m 50s
test ubuntu-latest nightly	2m 52s
feature-checks	3m 48s
docs	2m 1s
fmt	14s
test ubuntu-latest 1.76 --no-default-features	59s
no-std	31s
wasm-unknown	1m 2s
wasm-wasi	1m 38s
test ubuntu-latest 1.76	48s
test windows-latest stable --no-default-features	3m 38s
test windows-latest stable	3m 57s
test windows-latest nightly --no-default-features	6m 12s
test windows-latest nightly	6m 6s
test windows-latest 1.76 --no-default-features	2m 33s
test windows-latest 1.76	2m 23s
test ubuntu-latest stable --all-features	2m 13s
test ubuntu-latest nightly --all-features	3m 14s
	54m 5s

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