Restart broker without proxy churn measurements

Now that the proxy churn code has been removed (#40280 (closed)), we need to restart the broker with the new code. Then we can can call the current log file complete and ready it for publication.

The file /etc/runit/snowflake-broker/run needs to be edited to remove -ip-count-* options.

The key in -ip-count-mask needs to be destroyed. One difficulty here is that the /etc directory on the broker is version-controlled using etckeeper (Git). It is necessary to remove the key not only from the file /etc/runit/snowflake-broker/run but also from the version history. That may require rewriting history with git rebase -i, followed by git gc.