Avoid unused async when context manager includes `TaskGroup` #31213

Job	Run time
Determine changes	9s
pre-commit	35s
cargo fmt	21s
mkdocs	2m 31s
python package	1m 14s
cargo clippy	1m 38s
benchmarks	4m 58s
cargo build (msrv)	2m 57s
cargo build (release)	4m 39s
cargo fuzz	4m 37s
cargo shear	26s
cargo test (linux)	3m 21s
cargo test (wasm)	1m 10s
cargo test (windows)	7m 54s
formatter instabilities and black similarity	0s
test scripts	1m 2s
test ruff-lsp	15s
ecosystem	8m 40s
Fuzz the parser	0s
	46m 27s

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