[stubsabot] Bump singledispatch to 4.0.* (#9447)

Release: https://pypi.org/pypi/singledispatch/4.0.0
Homepage: https://github.com/jaraco/singledispatch
Diff: https://github.com/jaraco/singledispatch/compare/v3.7.0...v4.0.0

Stubsabot analysis of the diff between the two releases:
 - Total lines of Python code added: 381.
 - Total lines of Python code deleted: 266.

If stubtest fails for this PR:
- Leave this PR open (as a reminder, and to prevent stubsabot from opening another PR)
- Fix stubtest failures in another PR, then close this PR

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Co-authored-by: stubsabot <>

stubs/singledispatch/METADATA.toml

@@ -1,4 +1,4 @@
-version = "3.7.*"
+version = "4.0.*"
 
 [tool.stubtest]
 ignore_missing_stub = false