[stubsabot] Bump regex to 2025.9.18

Release: https://pypi.org/pypi/regex/2025.9.18
Homepage: https://github.com/mrabarnett/mrab-regex
Repository: https://github.com/mrabarnett/mrab-regex
Typeshed stubs: https://github.com/python/typeshed/tree/main/stubs/regex
Diff: mrabarnett/mrab-regex@2025.9.1...2025.9.18

Stubsabot analysis of the diff between the two releases:
 - Total lines of Python code added: 9.
 - Total lines of Python code deleted: 1.

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Author: stubsabot

stubs/regex/METADATA.toml

@@ -1,2 +1,2 @@
-version = "2025.9.1"
+version = "2025.9.18"
 upstream_repository = "https://github.com/mrabarnett/mrab-regex"