chore: Don't flex and don't install bison in CI image (#2210)

Test in: https://github.com/XRPLF/clio/pull/2211

docker/ci/Dockerfile

@@ -33,10 +33,8 @@ RUN apt-get update \
 # Install packages
 RUN apt-get update \
     && apt-get install -y --no-install-recommends --no-install-suggests \
-        bison \
         clang-tidy-${LLVM_TOOLS_VERSION} \
         clang-tools-${LLVM_TOOLS_VERSION} \
-        flex \
         git \
         git-lfs \
         graphviz \