Update cachetools requirement from <5,>=4 to >=4,<6

Updates the requirements on [cachetools](https://github.com/tkem/cachetools) to permit the latest version.
- [Release notes](https://github.com/tkem/cachetools/releases)
- [Changelog](https://github.com/tkem/cachetools/blob/master/CHANGELOG.rst)
- [Commits](tkem/cachetools@v4.0.0...v5.0.0)

---
updated-dependencies:
- dependency-name: cachetools
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

setup.cfg

@@ -42,7 +42,7 @@ install_requires =
     matplotlib
     scipy
     deprecation>=2.0.6
-    cachetools>=4,<5
+    cachetools>=4,<6
 python_requires = >=3.8
 
 [bdist_wheel]