Update Dockerfile

Dockerfile

@@ -24,7 +24,7 @@ RUN echo "ttf-mscorefonts-installer msttcorefonts/accepted-mscorefonts-eula sele
         ttf-mscorefonts-installer \
         fonts-freefont-ttf \
         fontconfig && \
-    wget -O /usr/share/fonts/xits-math.otf https://github.com/khaledhosny/xits-math/raw/master/XITSMath-Regular.otf
+    wget -O /usr/share/fonts/xits-math.otf https://github.com/khaledhosny/xits-math/raw/master/XITSMath-Regular.otf && \
     echo "Update font cache." && \
     fc-cache -fv && \
     echo "Delete TeX Live sources and other useless stuff." && \