fix(pg): Remove SIGINT capture and allow default node clean up (#1687)

This is to address an issue when using a private db for more than 10 minutes,
and ctrl+c fails to exit. This commit removes an empty handler for SIGINT
which ends up preventing the default handling.

https://heroku.support/939668

packages/pg-v5/lib/psql.js

@@ -76,21 +76,14 @@ function psqlInteractive (dbEnv, prompt) {
   })
 }
 
-function handleSignals () {
-  process.removeAllListeners('SIGINT')
-  process.on('SIGINT', () => {})
-}
-
 function * exec (db, query) {
-  handleSignals()
   let configs = bastion.getConfigs(db)
 
   yield bastion.sshTunnel(db, configs.dbTunnelConfig)
   return yield execPsql(query, configs.dbEnv)
 }
 
 async function execFile (db, file) {
-  handleSignals()
   let configs = bastion.getConfigs(db)
 
   await bastion.sshTunnel(db, configs.dbTunnelConfig)
@@ -100,7 +93,6 @@ async function execFile (db, file) {
 function * interactive (db) {
   let name = db.attachment.name
   let prompt = `${db.attachment.app.name}::${name}%R%# `
-  handleSignals()
   let configs = bastion.getConfigs(db)
   configs.dbEnv.PGAPPNAME = 'psql interactive' // default was 'psql non-interactive`