Merge #3938

3938: Switch to clamav's base image r=nextgens a=nextgens

## What type of PR?

bug-fix

## What does this PR do?

Use clamav's lighter base-image

### Related issue(s)
- closes #3937

## Prerequisites
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.

- [ ] 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/workflow.html#changelog) entry file.


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

setup/flavors/compose/docker-compose.yml

@@ -217,7 +217,7 @@ services:
   # Optional services
   {% if antivirus_enabled %}
   antivirus:
-    image: clamav/clamav-debian:1.4
+    image: clamav/clamav-debian:1.4_base
     restart: always
     logging:
       driver: journald

towncrier/newsfragments/3937.bugfix

@@ -0,0 +1 @@
+Use clamav's lighter base-image