plasmacalendarintegration: Omit astronomical events from Holidays data
These events aren't holidays, and because they're currently shown by the Holidays plugin, they get duplicated when you also have the Astronomical Events plugin enabled. It makes sense that if you want to see astronomical events, you'd use the Astronomical Events plugin, so let's not show those events in the Holidays plugin.
BUG: 465539 FIXED-IN: 5.27.1
(cherry picked from commit 16aca7fc)