Update h2 requirement from ==3.* to >=3,<5 (#208)

Updates the requirements on [h2](https://github.com/python-hyper/hyper-h2) to permit the latest version.
- [Release notes](https://github.com/python-hyper/hyper-h2/releases)
- [Changelog](https://github.com/python-hyper/hyper-h2/blob/master/CHANGELOG.rst)
- [Commits](python-hyper/h2@v3.0.0...v4.0.0)

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

setup.py

@@ -55,7 +55,7 @@ def get_packages(package):
     zip_safe=False,
     install_requires=["h11>=0.8,<0.10", "sniffio==1.*"],
     extras_require={
-        "http2": ["h2==3.*"],
+        "http2": ["h2>=3,<5"],
     },
     classifiers=[
         "Development Status :: 3 - Alpha",