Remove fixed PUBLIC_URL in Dockerfile

Change-Id: Ifb2e41f02f6568fd80fe9de4c76b633236ceffe4

Dockerfile

@@ -1,14 +1,13 @@
 # Builder
 FROM node:lts as builder
 
-ARG PUBLIC_URL=/
 ARG REACT_APP_SERVER
 
 WORKDIR /src
 
 COPY . /src
 RUN yarn --network-timeout=300000 install
-RUN PUBLIC_URL=$PUBLIC_URL REACT_APP_SERVER=$REACT_APP_SERVER yarn build
+RUN REACT_APP_SERVER=$REACT_APP_SERVER yarn build
 
 
 # App

docker-compose.yml

@@ -16,7 +16,7 @@ services:
     # if you're building on an architecture other than amd64, make sure
     # to define a maximum ram for node. otherwise the build will fail.
     #   - NODE_OPTIONS="--max_old_space_size=1024"
-    # default is /
+    # default is .
     #   - PUBLIC_URL=/synapse-admin
     # You can use a fixed homeserver, so that the user can no longer
     # define it himself