Float atomic operations doc fix #1481

Job	Run time
Test (macOS-latest)	11m 42s
Android (ubuntu-latest, aarch64-linux-android)	8m 55s
Compiletest (windows-latest)	17m 27s
Difftest (windows-latest)	22m 27s
Difftest (ubuntu-latest)	11m 49s
Lint	6m 0s
cargo-deny	1m 2s
Difftest (macOS-latest)	16m 50s
Test (ubuntu-latest)	12m 19s
Test (windows-latest)	22m 8s
Compiletest (macOS-latest)	10m 54s
Compiletest (ubuntu-latest)	8m 24s
test_success	3s
	2h 30m 0s

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