CI: Remove custom Linux deps and SwiftShader

The default environment already includes everything we need to build
all our configurations.

Remove custom SwiftShader setup as lavapipe should now be good enough,
but we need to install the latest one.

.github/workflows/static_checks.yml

@@ -13,17 +13,11 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v3
 
-      # Azure repositories are not reliable, we need to prevent Azure giving us packages.
-      - name: Make apt sources.list use the default Ubuntu repositories
+      - name: Install dependencies
         run: |
-          sudo rm -f /etc/apt/sources.list.d/*
-          sudo cp -f misc/ci/sources.list /etc/apt/sources.list
           wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
           sudo apt-add-repository "deb http://apt.llvm.org/focal/ llvm-toolchain-focal-15 main"
           sudo apt-get update
-
-      - name: Install dependencies
-        run: |
           sudo apt-get install -qq dos2unix clang-format-15 libxml2-utils python3-pip moreutils
           sudo update-alternatives --remove-all clang-format || true
           sudo update-alternatives --install /usr/bin/clang-format clang-format /usr/bin/clang-format-15 100