plugins: Remove 3.0 and add 3.3

The matrix needs to be updated with the release of 3.3 and new
stable-3.3 branches.

Remove the now EOL 3.0 column, while still keeping the 2.16 one, as it
is the last 2.x version that can be shown.

Change-Id: I090c29100b1b925b62a41ec93fe10902c4bc82a8
1 file changed