Improve migration document #40349

Job	Run time
Determine changes	9s
cargo build (release)	0s
mkdocs	2m 27s
cargo fmt	18s
pre-commit	3m 16s
python package	1m 17s
cargo fuzz build	0s
benchmarks	0s
cargo clippy	0s
cargo build (msrv)	0s
cargo shear	0s
cargo test (linux)	0s
cargo test (linux, release)	0s
cargo test (wasm)	0s
cargo test (windows)	0s
formatter instabilities and black similarity	0s
test scripts	0s
test ruff-lsp	0s
ecosystem	0s
fuzz parser	0s
	7m 27s

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