Fix space after newline character on php packages in generated Dockerfile

Fixes #366

Author: luispabon

src/PHPDocker/Template/dockerfile-php-fpm.conf.twig

@@ -4,7 +4,7 @@ WORKDIR "{{ dockerWorkingDir }}"
 {% if packages %}
 RUN apt-get update \
     && apt-get -y --no-install-recommends install \
-        {{ packages | join(' \\ \n        ') }} \
+        {{ packages | join(' \\\n        ') }} \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/* /usr/share/doc/*
 {% endif %}