Fix error message when subclassing TypeVarTuple #2408

Job	Run time
Run tests (3.9.12)	23s
Run tests (3.9)	21s
Run tests (3.10)	20s
Run tests (3.11)	22s
Run tests (3.11.0)	21s
Run tests (pypy3.9)	29s
Run tests (3.12)	19s
Run tests (3.12.0)	22s
Run tests (3.13.0)	21s
Run tests (3.14)	23s
Run tests (pypy3.10)	30s
Run tests (pypy3.11)	26s
Run tests (3.13)	23s
Run tests (3.10.4)	20s
Create an issue if daily tests failed	0s
	5m 20s

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