GitHub Actions: stop passing sysctl flag for ipv6

Author: rjbs

.github/workflows/main.yml

@@ -17,7 +17,7 @@ jobs:
     runs-on: ubuntu-latest
     container:
         image: cyrusimapdocker/cyrus-bookworm:latest
-        options: --sysctl net.ipv6.conf.all.disable_ipv6=0 --init
+        options: --init
     steps:
     - uses: actions/checkout@v4
       with: