Modernize to hubot 14 (ESM)

- hubot 14.1.0; @hubot-friends/hubot-irc ^2.0.2; hubot-redis-brain 3.0.1
  (exact pin); hubot-help ^2.1.5; hubot-remotestorage-logger (git branch)
- drop hubot-irc, coffee-script, request, hubot-web-push-notifications, and the
  unused hubot-xmpp / hubot-incoming-webhook / hubot-auth / cheerio (they drag
  in node-xmpp-client, request and coffee-script)
- scripts/health.js -> ESM; delete scripts/example.coffee
- external-scripts.json: hubot-help, hubot-redis-brain,
  hubot-remotestorage-logger
- Procfile / run.sh: -a @hubot-friends/hubot-irc

The hubot-remotestorage-logger dep points at the feature/hubot-14 branch until
67P/hubot-remotestorage-logger#5 is merged and v2.0.0 is tagged on master.

external-scripts.json

@@ -1,6 +1,5 @@
 [
   "hubot-help",
-  "hubot-remotestorage-logger",
   "hubot-redis-brain",
-  "hubot-web-push-notifications"
+  "hubot-remotestorage-logger"
 ]