[ty] Avoid diagnostic when `typing_extensions.ParamSpec` uses `default` parameter #58855

Job	Run time
python package	1m 35s
pre-commit	2m 1s
cargo fmt	19s
mkdocs	2m 58s
Determine changes	20s
cargo clippy	2m 1s
cargo test (linux)	4m 18s
cargo test (linux, release)	4m 13s
cargo test (macos-latest)	9m 0s
cargo test (depot-windows-2022-16)	7m 31s
cargo test (wasm)	3m 36s
cargo build (msrv)	2m 0s
check playground	-1s
cargo fuzz build	5m 9s
benchmarks walltime (medium\|multithreaded)	16m 24s
benchmarks instrumented (ruff)	-1s
benchmarks walltime (small\|large)	16m 42s
ecosystem	1m 48s
test scripts	1m 3s
benchmarks instrumented (ty)	9m 50s
test ruff-lsp	3m 4s
cargo shear	26s
Fuzz for new ty panics	4m 49s
formatter instabilities and black similarity	-1s
ty completion evaluation	1m 57s
fuzz parser	-1s
	1h 41m 0s

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