Bump Etherpad version

pica-etherpad/Dockerfile

@@ -2,7 +2,7 @@
 FROM node:10-slim as base
 LABEL maintainer="antoine@barbare.me"
 
-ARG ETHERPAD_VERSION_BUILD=1.7.0
+ARG ETHERPAD_VERSION_BUILD=1.7.5
 ARG ETHERPAD_LANDING_PAGE_VERSION_BUILD=v0.1
 ARG NODE_ENV_BUILD=production
 

pica-etherpad/docker-compose.yml

 version : "2.4"
 services:
     etherpad-app:
-        image: pica-etherpad:1.7.0
+        image: pica-etherpad:1.7.5
         container_name: etherpad-app
         links:
           - etherpad-db:mysql