Remove ubuntu ppa

.github/workflows/dependencies/dependencies_gcc.sh

@@ -12,7 +12,6 @@ set -eu -o pipefail
 #   failed files the given number of times.
 echo 'Acquire::Retries "3";' | sudo tee /etc/apt/apt.conf.d/80-retries
 
-sudo add-apt-repository ppa:ubuntu-toolchain-r/test
 sudo apt-get update
 
 sudo apt-get install -y --no-install-recommends \