Replace apt-fast with apt-get (#159)

`apt-fast` was removed from GitHub with Ubuntu 24.04:

- actions/runner-images#10003

For compatibility, switch back to `apt-get`.

.github/workflows/ci.yml

@@ -44,19 +44,12 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
 
-      - name: Set GCC 10 as default compiler (Linux)
-        if: runner.os == 'Linux' && matrix.target.cpu != 'i386'
-        run: |
-          sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-10 100 \
-            --slave /usr/bin/g++ g++ /usr/bin/g++-10 \
-            --slave /usr/bin/gcov gcov /usr/bin/gcov-10
-
       - name: Install build dependencies (Linux i386)
         if: runner.os == 'Linux' && matrix.target.cpu == 'i386'
         run: |
           sudo dpkg --add-architecture i386
-          sudo apt-fast update -qq
-          sudo DEBIAN_FRONTEND='noninteractive' apt-fast install \
+          sudo apt-get update -qq
+          sudo DEBIAN_FRONTEND='noninteractive' apt-get install \
             --no-install-recommends -yq gcc-10-multilib g++-10-multilib \
             libssl-dev:i386 linux-libc-dev:i386
           mkdir -p external/bin