Purge gcc-10 from Ubuntu CI builds

Looks like its headers break indexstore-db build

Author: MaxDesiatov

.github/workflows/main.yml

@@ -19,7 +19,7 @@ jobs:
       - name: Free disk space
         run: |
           df -h
-          sudo apt-get purge libgcc-9-dev gcc-9 libstdc++-9-dev
+          sudo apt-get purge libgcc-9-dev gcc-9 libstdc++-9-dev gcc-10 libgcc-10-dev
           sudo swapoff -a
           sudo rm -f /swapfile
           sudo rm -rf /opt/hostedtoolcache
@@ -69,6 +69,7 @@ jobs:
         run: |
           df -h
           sudo swapoff -a
+          sudo apt-get purge gcc-10 libgcc-10-dev
           sudo rm -f /swapfile
           sudo rm -rf /opt/hostedtoolcache
           sudo rm -rf /usr/share/dotnet