Bump icalendar from 4.0.6 to 4.0.7 (#1012)

Bumps [icalendar](https://github.com/collective/icalendar) from 4.0.6 to 4.0.7.
- [Release notes](https://github.com/collective/icalendar/releases)
- [Changelog](https://github.com/collective/icalendar/blob/master/CHANGES.rst)
- [Commits](https://github.com/collective/icalendar/compare/4.0.6...4.0.7)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

requirements.txt

@@ -10,7 +10,7 @@ python-Levenshtein>=0.12.0
 pytz>=2018.9
 whatthepatch>=0.0.5
 icalevents==0.1.25
-icalendar==4.0.6
+icalendar==4.0.7
 sqlalchemy==1.3.19
 filelock==3.0.12
 alembic==1.4.3