Fix error message when subclassing TypeVarTuple #2400

Job	Run time
Run tests (3.9)	10s
Run tests (3.11)	15s
Run tests (3.10)	10s
Run tests (3.10.4)	19s
Run tests (pypy3.10)	21s
Run tests (3.11.0)	19s
Run tests (3.13.0)	22s
Run tests (3.12)	21s
Run tests (3.12.0)	21s
Run tests (pypy3.11)	23s
Run tests (pypy3.9)	23s
Run tests (3.13)	20s
Run tests (3.14)	23s
Run tests (3.9.12)	18s
Create an issue if daily tests failed	0s
	4m 25s

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