Update icalendar requirement from <4.1,>=4.0.3 to >=4.0.3,<5.1 (#1947)

Updates the requirements on [icalendar](https://github.com/collective/icalendar) to permit the latest version.
- [Release notes](https://github.com/collective/icalendar/releases)
- [Changelog](https://github.com/collective/icalendar/blob/master/CHANGES.rst)
- [Commits](collective/icalendar@4.0.3...v5.0.12)

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

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

server/requirements.txt

@@ -7,7 +7,7 @@ pydocstyle<4.0
 wooper==0.4.4
 requests
 requests-mock==1.12.1
-icalendar>=4.0.3,<4.1
+icalendar>=4.0.3,<5.1
 coverage==7.4.4
 deepdiff
 coveralls

setup.py

@@ -25,7 +25,7 @@
     author="Edouard Richard",
     author_email="[email protected]",
     license="AGPLv3",
-    install_requires=["icalendar>=4.0.3,<4.1", "deepdiff"],
+    install_requires=["icalendar>=4.0.3,<5.1", "deepdiff"],
     url="https://github.com/superdesk/superdesk-planning",
     classifiers=[
         "Development Status :: 5 - Production/Stable",