Update Dockerfile

Missed adding && \

Author: robe2

Dockerfile

@@ -75,7 +75,7 @@ RUN git clone --depth 1 --branch ${PROJ_BRANCH} https://github.com/OSGeo/PROJ &&
     cmake .. && \
     make -j${BUILD_THREADS} && \
     make install && \
-    projsync --system-directory
+    projsync --system-directory && \
     cd /src && rm -rf PROJ
 
 ARG BUILD_DATE