Fix resolving flexible lengths (WPT css/flexbox-multiline-min-max tes… #2270

Job	Run time
Build [debug feature]	7s
Test Suite [default features]	1m 27s
Test Suite [default + serde]	1m 50s
MSRV Build [Rust 1.65]	2m 18s
Test Suite [std (no algorithms)]	1m 34s
Test Suite [no features]	1m 37s
Test Suite [alloc + all algorithms]	1m 31s
Test Suite [std + block)]	1m 26s
Test Suite [default except content_size]	1m 37s
Test Suite [std + flexbox]	1m 36s
Test Suite [std + grid]	1m 26s
Test Suite [alloc + no algorithms]	1m 38s
Build Benchmarks	31s
Build Benchmarks (w/ yoga)	47s
Clippy	30s
Documentation	27s
Test Fixture Formatting	9s
Rustfmt	7s
Markdown Lint	5s
	20m 43s

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