Remove "Beta" Label from formatter documentation #25125

Job	Run time
mkdocs	2m 18s
Determine changes	7s
pre-commit	51s
cargo fmt	18s
python package	1m 10s
benchmarks	4m 41s
cargo clippy	2m 34s
cargo fuzz	5m 5s
cargo test (linux)	3m 37s
cargo test (wasm)	1m 24s
cargo test (windows)	5m 41s
formatter instabilities and black similarity	3m 47s
cargo udeps	1m 58s
test scripts	50s
test ruff-lsp	20s
ecosystem	5m 44s
	40m 25s

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