Revert "Adding ICS for calendar download"

This reverts commit a17ee4f.

Author: ckenst

README.md

@@ -78,15 +78,6 @@ This versioning system enables:
 - Associating bug reports with specific deployments
 - Measuring quality metrics across versions (see [ROADMAP.md](ROADMAP.md))
 
-## Calendar (.ics) Export
-
-Generate a downloadable calendar file from `_data/current.yml`:
-
-```shell
-ruby tools/generate_calendar_ics.rb
-```
-
-This writes `calendar.ics` at the repository root.
 
 ## License