Replace `apt-fast` with `apt-get` (#34)

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

- https://github.com/actions/runner-images/issues/10003

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

.github/workflows/ci.yml

@@ -65,8 +65,8 @@ jobs:
         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-multilib g++-multilib \
             libssl-dev:i386
           mkdir -p external/bin