CI: GCC 13 install fails, so disable that particular ppa

closes: #17149

Signed-off-by: Philip H. <47042125+pheiduck@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b35c3b6..fc6cd96 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -21,7 +21,7 @@
 
     env:
       CC: ${{ matrix.compiler }}
-      GCC_VER: 13
+      GCC_VER: 14
       CLANG_VER: 20
       TEST: test
       SRCDIR: ./src
@@ -149,7 +149,8 @@
         if:  matrix.compiler == 'gcc'
         run: |
           # ubuntu-toolchain-r/test PPA for gcc-13 compiler
-          sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
+          # disabled because the installation failed, causing test failures
+          # sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
           sudo apt-get update -y
           sudo apt-get install -y gcc-${{ env.GCC_VER }}:${{ matrix.architecture }}
           sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-${{ env.GCC_VER }} 100