Removed empty continuation lines

Remove empty continuation lines to avoid errors in a future release

Dockerfile

@@ -1,18 +1,13 @@
 FROM debian:buster
 
-  
+#Install dependencies, add proxmox repo and install packages
 RUN apt-get update && \
-  #Install dependencies
   apt-get install -y \
   wget \
   ca-certificates \
   && rm -rf /var/lib/apt/lists/* && \
-  
-  #Add repository
   echo "deb http://download.proxmox.com/debian/pbs buster pbstest" > /etc/apt/sources.list.d/pbstest-beta.list && \
   wget http://download.proxmox.com/debian/proxmox-ve-release-6.x.gpg -O /etc/apt/trusted.gpg.d/proxmox-ve-release-6.x.gpg && \
-
-  #Install packages
   apt-get update && \
   apt-get install -y proxmox-backup-server=0.9.6-1