Update rocket.chat

Changes:

- https://github.com/RocketChat/Docker.Official.Image/commit/dff5cad: Update to 2.0.0

library/rocket.chat

@@ -1,5 +1,5 @@
 Maintainers: Rocket.Chat Image Team <[email protected]> (@RocketChat)
 GitRepo: https://github.com/RocketChat/Docker.Official.Image.git
 
-Tags: 1.3.2, 1.3, 1, latest
-GitCommit: ce9eb5644998ef22ed4980b79a0543bd9998df71
+Tags: 2.0.0, 2.0, 2, latest
+GitCommit: dff5cadb2b10bad4b060b879bcfc5db531ebc82a