Merge pull request #15068 from overleaf/bg-server-pro-add-xetex

add xetex to the base image for CE/SP

GitOrigin-RevId: 2967872957d0def48071ee66293a029e1b91e60a

server-ce/Dockerfile-base

@@ -66,7 +66,7 @@ RUN mkdir /install-tl-unx \
       texcount \
       synctex \
       etoolbox \
-    \
+      xetex \
 &&  tlmgr path add \
 &&  rm -rf /install-tl-unx