[red-knot] Do not panic on f-string format spec expressions #35902

Job	Run time
mkdocs	2m 40s
pre-commit	42s
cargo fmt	16s
Determine changes	13s
python package	1m 42s
cargo test (linux)	4m 15s
cargo test (wasm)	1m 32s
cargo build (msrv)	4m 14s
cargo clippy	1m 52s
cargo fuzz	5m 4s
cargo build (release)	8m 25s
cargo test (windows)	7m 13s
benchmarks	4m 51s
cargo shear	41s
test scripts	1m 4s
formatter instabilities and black similarity	0s
ecosystem	8m 57s
test ruff-lsp	35s
Fuzz the parser	0s
	54m 16s

Provide feedback