Fix continuation detection following multi-line strings #23081

Job	Run time
mkdocs	2m 5s
Determine changes	8s
pre-commit	35s
cargo fmt	16s
python package	1m 7s
cargo clippy	1m 51s
cargo test (wasm)	1m 16s
cargo test (linux)	3m 36s
cargo test (windows)	5m 24s
test scripts	47s
cargo fuzz	3m 32s
cargo udeps	1m 59s
formatter instabilities and black similarity	3m 48s
benchmarks	6m 10s
ecosystem	11m 28s
test ruff-lsp	16s
	44m 18s

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