Update cython requirement from <1 to <4 in /sdks/python

Updates the requirements on [cython](https://github.com/cython/cython) to permit the latest version.
- [Release notes](https://github.com/cython/cython/releases)
- [Changelog](https://github.com/cython/cython/blob/master/CHANGES.rst)
- [Commits](cython/cython@0.9.6.14...3.0.10)

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

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

sdks/python/container/base_image_requirements_manual.txt

@@ -27,7 +27,7 @@
 bs4  # Commonly used HTML processing tool.
 # Don't upgrade to Cython 3.x, until it's released, stable and we have consensus
 # to upgrade. Use 0.xx for now.
-cython<1
+cython<4
 # future is no longer a Beam dependency, but is an implicit dependency in
 # some versions of libraries that lauch Beam pipelines, like tensorflow-transform.
 # Leaving 'future' in our containers for now prevent breaking tft users.