build(deps): update packaging requirement from <25 to <26

Updates the requirements on [packaging](https://github.com/pypa/packaging) to permit the latest version.
- [Release notes](https://github.com/pypa/packaging/releases)
- [Changelog](https://github.com/pypa/packaging/blob/main/CHANGELOG.rst)
- [Commits](pypa/packaging@14.0...25.0)

---
updated-dependencies:
- dependency-name: packaging
  dependency-version: '25.0'
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements.txt

@@ -1,2 +1,2 @@
 slack_bolt>=1.18.0,<2
-packaging<25
+packaging<26