Reduce default crispin connection pool size to 4.
Reduce default crispin connection pool size to 4.

Pretty sure this is still a safe number. We can probably go lower, but should
check that first.

EthanBlackburn/sync-engine,PriviPK/privipk-sync-engine,gale320/sync-engine,PriviPK/privipk-sync-engine,ErinCall/sync-engine,PriviPK/privipk-sync-engine,jobscore/sync-engine,EthanBlackburn/sync-engine,gale320/sync-engine,wakermahmud/sync-engine,jobscore/sync-engine,ErinCall/sync-engine,Eagles2F/sync-engine,closeio/nylas,gale320/sync-engine,gale320/sync-engine,nylas/sync-engine,ErinCall/sync-engine,Eagles2F/sync-engine,closeio/nylas,jobscore/sync-engine,nylas/sync-engine,wakermahmud/sync-engine,nylas/sync-engine,wakermahmud/sync-engine,ErinCall/sync-engine,closeio/nylas,Eagles2F/sync-engine,nylas/sync-engine,jobscore/sync-engine,wakermahmud/sync-engine,gale320/sync-engine,wakermahmud/sync-engine,closeio/nylas,Eagles2F/sync-engine,ErinCall/sync-engine,Eagles2F/sync-engine,PriviPK/privipk-sync-engine,EthanBlackburn/sync-engine,PriviPK/privipk-sync-engine,EthanBlackburn/sync-engine,EthanBlackburn/sync-engine