Merge #1845

1845: Update rainloop to 1.16.0 r=mergify[bot] a=nextgens

## What type of PR?

Security-update for rainloop.

## What does this PR do?

Upgrade to rainloop v1.16

### Related issue(s)
- #1829

## Prerequistes
Before we can consider review and merge, please make sure the following list is done and checked.
If an entry in not applicable, you can check it or remove it from the list.

- [x] In case of feature or enhancement: documentation updated accordingly
- [x] Unless it's docs or a minor change: add [changelog](https://mailu.io/master/contributors/guide.html#changelog) entry file.


Co-authored-by: Florent Daigniere <nextgens@freenetproject.org>

towncrier/newsfragments/1845.feature

@@ -0,0 +1 @@
+Update version of rainloop webmail to 1.16.0. This is a security update.

webmails/rainloop/Dockerfile

@@ -17,7 +17,7 @@ RUN apt-get update && apt-get install -y \
 # Shared layer between nginx, dovecot, postfix, postgresql, rspamd, unbound, rainloop, roundcube
 RUN pip3 install socrate
 
-ENV RAINLOOP_URL https://github.com/RainLoop/rainloop-webmail/releases/download/v1.14.0/rainloop-community-1.14.0.zip
+ENV RAINLOOP_URL https://github.com/RainLoop/rainloop-webmail/releases/download/v1.16.0/rainloop-community-1.16.0.zip
 
 RUN apt-get update && apt-get install -y \
       unzip python3-jinja2 \