[hotfix] bump socket pool to 5

context:

• as a test to see if it would result in fewer concurrency bugs in signald, we dropped the signalboost socket pool size from 50 to 1
• over a 5 day period, we observed only 1 channel crash (fixable by restarting), but we saw average message delivery latency jump from around 50ms-1sec to 30-60sec.
• we also saw ~10 false positive failed health checks per day

change:

• as an experiement to see if we can bring delivery latency down (and reduce false positives) without drastically increasing crashes, we are going to raise the socket pool size from 1 to 5 and observe the effects for 5 days