[ci] enable memory swapping to avoid OOM in container

Author: kateinoigakukun

.github/workflows/build-toolchain.yml

@@ -96,8 +96,6 @@ jobs:
         if: ${{ matrix.free_disk_space }}
         run: |
           df -h
-          sudo swapoff -a
-          sudo rm -f /swapfile
           sudo rm -rf /opt/hostedtoolcache
           sudo rm -rf /usr/share/dotnet
           sudo apt clean