Update iso8601 requirement from ~=0.1.16 to >=0.1.16,<1.1.0

Updates the requirements on [iso8601](https://github.com/micktwomey/pyiso8601) to permit the latest version.
- [Release notes](https://github.com/micktwomey/pyiso8601/releases)
- [Commits](micktwomey/pyiso8601@0.1.16...1.0.0)

---
updated-dependencies:
- dependency-name: iso8601
  dependency-type: direct:production
...

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

setup.py

@@ -16,7 +16,7 @@
     packages=setuptools.find_packages(),
     install_requires=[
         "requests",
-        "iso8601~=0.1.16",
+        "iso8601>=0.1.16,<1.1.0",
         "pytz~=2021.1",
         "tzlocal>=2.1,<3.0",
         "deprecation~=2.1.0",