Fix incorrect TypingUnionType import check #9519

Job	Run time
📈 Benchmarks	3m 32s
✨ Lint	2m 4s
🪟 Tests on Windows	4m 49s
💻 Generate test matrix	25s
🔬 Tests on 3.12	5m 48s
🔬 Tests on 3.11	2m 30s
🔬 Tests on 3.10	2m 4s
🔬 Tests on 3.9	1m 57s
🔬 Tests on 3.8	1m 56s
🔬 Django tests on 3.11 (django=4.2.0)	1m 36s
🔬 Django tests on 3.11 (django=4.1.0)	1m 34s
🔬 Django tests on 3.11 (django=4.0.0)	1m 43s
🔬 Django tests on 3.11 (django=3.2.0)	2m 0s
🔬 Starlette tests on 3.11 (starlette=0.28.0)	1m 35s
🔬 Starlette tests on 3.11 (starlette=0.27.0)	1m 47s
🔬 Starlette tests on 3.11 (starlette=0.26.1)	1m 32s
🔬 Test integrations on 3.11 (integration=aiohttp)	1m 36s
🔬 Test integrations on 3.11 (integration=chalice)	1m 57s
🔬 Test integrations on 3.11 (integration=channels)	1m 59s
🔬 Test integrations on 3.11 (integration=fastapi)	1m 26s
🔬 Test integrations on 3.11 (integration=flask)	1m 38s
🔬 Test integrations on 3.11 (integration=sanic)	1m 46s
🔬 Test integrations on 3.11 (integration=starlite)	2m 6s
🔬 Pydantic tests on 3.11 (pydantic=1.10)	1m 22s
🔬 Pydantic tests on 3.11 (pydantic=2.0.3)	1m 22s
🔬 Pyright tests on 3.12	5m 43s
🔬 Pyright tests on 3.11	2m 18s
🔬 Pyright tests on 3.10	2m 34s
🔬 Pyright tests on 3.9	1m 55s
🔬 Pyright tests on 3.8	2m 6s
🔬 CLI tests on 3.12	4m 43s
🔬 CLI tests on 3.11	1m 52s
🔬 CLI tests on 3.10	1m 34s
🔬 CLI tests on 3.9	1m 46s
🔬 CLI tests on 3.8	1m 38s
	1h 18m 13s

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