fix links in MIGRATE-2-to-3.md #2291

Job	Run time
Test	35s
Test	26s
Test (charset)	36s
cargo-deny (aarch64-apple-ios)	18s
Test (charset)	25s
build_versions (stable)	13s
cargo-deny (aarch64-linux-android)	17s
Test (cookies)	34s
Test (cookies)	45s
build_versions (beta)	17s
cargo-deny (i686-pc-windows-gnu)	20s
Test (socks-proxy)	31s
Test (socks-proxy)	48s
build_versions (1.67.0)	29s
cargo-deny (i686-pc-windows-msvc)	20s
Test (gzip)	30s
Test (gzip)	48s
cargo-deny (i686-unknown-linux-gnu)	22s
Test (brotli)	26s
Test (brotli)	41s
Test (json)	25s
Docs	46s
cargo-deny (wasm32-unknown-unknown)	19s
Test (json)	35s
Test (native-tls)	31s
cargo-deny (x86_64-apple-darwin)	18s
Test (native-tls)	46s
Lint	15s
cargo-deny (x86_64-apple-ios)	22s
cargo-deny (x86_64-pc-windows-gnu)	19s
cargo-deny (x86_64-pc-windows-msvc)	20s
cargo-deny (x86_64-unknown-linux-gnu)	19s
cargo-deny (x86_64-unknown-redox)	17s
	15m 13s

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