Update dependency icalendar to v5.0.12

This MR contains the following updates:

Package	Type	Update	Change
icalendar	dependencies	patch	5.0.11 -> 5.0.12

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Release Notes

collective/icalendar (icalendar)

v5.0.12

Compare Source

Minor changes:

• Analyse code coverage of test files
• Added corpus to fuzzing directory
• Added exclusion of fuzzing corpus in MANIFEST.in
• Augmented fuzzer to optionally convert multiple calendars from a source string
• Add script to convert OSS FUZZ test cases to Python/pytest test cases
• Added additional exception handling of defined errors to fuzzer, to allow fuzzer to explore deeper
• Added more instrumentation to fuzz-harness
• Rename "contributor" to "collaborator" in documentation
• Correct the outdated "icalendar view myfile.ics" command in documentation. #​588
• Update GitHub Actions steps versions
• Keep GitHub Actions up to date with GitHub's Dependabot

Breaking changes:

• ...

New features:

• ...

Bug fixes:

• ...
• Fixed index error in cal.py when attempting to pop from an empty stack
• Fixed type error in prop.py when attempting to join strings into a byte-string
• Caught Wrong Date Format in ical_fuzzer to resolve fuzzing coverage blocker

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