Fix dockerfile line ending

Author: kduma

Dockerfile

@@ -27,7 +27,7 @@ RUN apt-get update \
 	&& apt-get -y install cups-client \
     && apt-get -y autoremove \
     && apt-get clean \
-    && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/* \
+    && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
 
 RUN docker-php-ext-install sockets