[`pyupgrade`] Handle multiple base classes for PEP 695 generics (`UP0… #6

Job	Run time
cargo build (release)	8m 29s
mkdocs	4m 5s
Determine changes	11s
cargo fmt	22s
pre-commit	4m 54s
python package	2m 52s
cargo fuzz build	6m 28s
cargo clippy	4m 5s
benchmarks	0s
cargo build (msrv)	6m 59s
cargo shear	25s
cargo test (linux)	1s
cargo test (linux, release)	1s
cargo test (wasm)	2m 58s
cargo test (windows)	1s
formatter instabilities and black similarity	4m 54s
test scripts	2m 28s
test ruff-lsp	0s
ecosystem	0s
fuzz parser	0s
	49m 13s

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