contrib: Update plugin API version to match meson.build

This was missing from commit cea6300e.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
2 jobs for shared-library in 6 minutes and 19 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Build
passed debian-stable-x86_64 #1199888

00:02:35

passed fedora-x86_64 #1199887

00:06:19