Update Dockerfile

Dockerfile

@@ -10,5 +10,5 @@ RUN rustup component add clippy
 
 # Add libraries needed to compile dunitrust
 RUN apt-get update && \
-   apt-get install -y git pkg-config libssl-dev && \
+   apt-get install -y --no-install-recommends git pkg-config libssl-dev && \
    apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*