[hotfix] dial socket pool to 5 (temporarily)

• we are about to delete a large channel, which will yield interesting data on message lag when it sends out a notification of the deletion to all subscribers
• in order to measure the effects of socket pooling, we are going to temporarily increase the socket pool back to 5 in order to get APMs from the transmission, then dial it back to 1 (which results in fewer crashes due to concurrency issues in signald)