Bump libc6 version in linux workaround

In order to make linux builds work for now, we're
downgrading gcc. This workaround broke, seemingly
because the lib6 version got upgraded? Bumping the
version here fixes things.

.github/workflows/cmake_ctest.yml

@@ -54,7 +54,9 @@ jobs:
         sudo apt-get update && sudo apt install libasound2-dev libx11-dev libxinerama-dev libxext-dev libfreetype6-dev libwebkit2gtk-4.0-dev libglu1-mesa-dev xvfb fluxbox ninja-build
         # downgrade gcc to workaround 22.04 and C++20 issue
         # see: https://github.com/actions/runner-images/issues/8659
-        sudo apt-get install -y --allow-downgrades libc6=2.35-0ubuntu3.4 libc6-dev=2.35-0ubuntu3.4 libstdc++6=12.3.0-1ubuntu1~22.04 libgcc-s1=12.3.0-1ubuntu1~22.04
+        sudo rm -f /etc/apt/sources.list.d/ubuntu-toolchain-r-ubuntu-test-jammy.list
+        sudo apt-get update
+        sudo apt-get install -y --allow-downgrades libc6=2.35-0ubuntu3.5 libc6-dev=2.35-0ubuntu3.5 libstdc++6=12.3.0-1ubuntu1~22.04 libgcc-s1=12.3.0-1ubuntu1~22.04
         sudo /usr/bin/Xvfb $DISPLAY &
 
     # This lets us use sscache on Windows