docker: Stop installing python3-distutils

In Ubuntu 24.04, this package is no longer available.

However, this package probably never actually was needed anyway,
and was probably only provided as a convenience for users of the
docker image.

Dockerfile.system-clang

@@ -3,7 +3,7 @@ FROM ubuntu:22.04
 RUN apt-get update -qq && \
     DEBIAN_FRONTEND="noninteractive" apt-get install -qqy --no-install-recommends \
     git wget bzip2 file unzip libtool pkg-config cmake build-essential \
-    automake yasm gettext autopoint vim-tiny python3 python3-distutils \
+    automake yasm gettext autopoint vim-tiny python3 \
     ninja-build ca-certificates curl less zip && \
     apt-get clean -y && \
     rm -rf /var/lib/apt/lists/*