fix: properly wait for docs engine shutdown (#2389) #8710

Job	Run time
Cross Build Only (armv7-linux-androideabi)	1m 8s
check_semver	4m 7s
Cross Build Only (aarch64-linux-android)	1m 1s
Build wasm32	28s
Cross Build Only (x86_64-unknown-freebsd)	1m 8s
Cross Build Only (x86_64-unknown-netbsd)	1m 10s
cargo deny	32s
Checking docs	1m 35s
Checking fmt	21s
clippy_check	2m 26s
Cross Test (i686-unknown-linux-gnu)	2m 39s
Minimal Supported Rust Version	2m 24s
Run network simulations/benchmarks	7m 57s
CI Test Suite / Tests (ubuntu-latest, stable, all)	2m 38s
CI Test Suite / Tests (ubuntu-latest, stable, none)	2m 7s
CI Test Suite / Tests (ubuntu-latest, stable, default)	2m 7s
CI Test Suite / Tests (macOS-arm-latest, stable, all)	3m 10s
CI Test Suite / Tests (macOS-arm-latest, stable, none)	2m 53s
CI Test Suite / Tests (macOS-arm-latest, stable, default)	2m 53s
CI Test Suite / Tests (windows-latest, stable, all, x86_64-pc-windows-msvc)	3m 49s
CI Test Suite / Tests (windows-latest, stable, none, x86_64-pc-windows-msvc)	3m 55s
CI Test Suite / Tests (windows-latest, stable, default, x86_64-pc-windows-msvc)	3m 54s
	54m 22s

Provide feedback