Test `Affine::svd`, drop statement that singular matrices produce NaN… #683

Job	Run time
cargo clippy (wasm32)	44s
cargo check (msrv) (wasm32)	26s
cargo clippy (windows-latest)	1m 22s
cargo clippy (macos-latest)	42s
cargo doc	21s
cargo check (msrv) (windows-latest)	48s
cargo fmt	20s
cargo check (msrv) (macos-latest)	38s
cargo clippy (ubuntu-latest)	1m 8s
cargo check (msrv) (ubuntu-latest)	22s
cargo test (windows-latest)	55s
cargo test (wasm32)	17s
cargo test (macos-latest)	34s
typos	4s
cargo test (ubuntu-latest)	18s
	8m 59s

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