Fix typo

Dockerfile_ubuntu_bionic

@@ -53,7 +53,7 @@ RUN curl -sL http://storage-ci.web.cern.ch/storage-ci/storageci.key | apt-key ad
     && apt-get update \
     && echo "deb http://storage-ci.web.cern.ch/storage-ci/debian/xrootd bionic release\n# deb-src http://storage-ci.web.cern.ch/storage-ci/debian/xrootd bionic release" >> /etc/apt/sources.list \
     && add-apt-repository 'deb http://storage-ci.web.cern.ch/storage-ci/debian/xrootd bionic release' \
-    && echo -e "Package: xrootd* libxrd* libxrootd*\nPin: version 4.12.3\nPin-Priority: 1000" > /etc/apt/preferences.d/xrootd.pref
+    && echo "Package: xrootd* libxrd* libxrootd*\nPin: version 4.12.3\nPin-Priority: 1000" > /etc/apt/preferences.d/xrootd.pref
 
 # Create local repo from eos artifacts
 ENV EOSREPODIR="/debs/eos/"