Remove docker socket mount (#2817)

Most uses of this mount point should have been refactored or removed.

buildkite/bazelci.py

diff --git a/buildkite/bazelci.py b/buildkite/bazelci.py
index 9cbc55f..1ca70dc 100755
--- a/buildkite/bazelci.py
+++ b/buildkite/bazelci.py
@@ -3265,7 +3265,6 @@
                     "/opt/android-sdk-linux:/opt/android-sdk-linux:ro",
                     "/var/lib/buildkite-agent:/var/lib/buildkite-agent",
                     "/var/lib/gitmirrors:/var/lib/gitmirrors:ro",
-                    "/var/run/docker.sock:/var/run/docker.sock",
                 ],
             }
         },