Remove unnecessary X- properties in sent VTIMEZONEs (for libical compatibility)

See https://github.com/libical/libical/pull/446
3 jobs for master in 7 minutes and 32 seconds
Status Job ID Name Coverage
  Test
passed #810005284
pages

00:04:55

passed #810005283
privileged
test

00:07:32

 
  Deploy
passed pages:deploy

00:00:04