vpx: Fix build against libvpx 1.8

The deprecated debug visualizer was removed.
9 jobs for libvpx-1.8 in 22 minutes and 1 second (queued for 2 seconds)
Status Job ID Name Coverage
  Preparation
passed #99912
gst indent

00:00:29

passed #99911
manifest

00:00:19

 
  Build
passed #99913
build fedora x86_64

00:03:09

 
  Test
passed #99914
check fedora

00:03:03

 
  Full Builds
passed #99915
build android arm64 api28

00:03:49

passed #99923
build cerbero cross win32

00:07:58

passed #99918
build cerbero cross win64

00:07:18

passed #99916
build cerbero fedora x86_64

00:07:14

failed #99917
build cerbero cross win32

00:01:08