Merge pull request #2126 from Fenrirthviti/linux-ci-fix

CI: Remove dead PPA to fix Linux build failure

CI/install-dependencies-linux.sh

@@ -1,7 +1,6 @@
 #!/bin/sh
 set -ex
 
-sudo add-apt-repository ppa:jonathonf/ffmpeg-3 -y
 curl -L https://packagecloud.io/github/git-lfs/gpgkey | sudo apt-key add -
 
 # gets us newer clang