Cleanup dupe python3 dependency

Author: bmhan12

docker/tpl-ubuntu-gcc.Dockerfile

@@ -122,7 +122,6 @@ RUN DEBIAN_FRONTEND=noninteractive TZ=America/Los_Angeles \
     git \
     ghostscript \
     ninja-build \
-    python3 \
     python3-dev \
     python3-mpi4py \
     python3-scipy \