Drop software-properties-common — removed from Debian trixie

The package no longer exists in trixie (was the cause of apt-get exit
100: "Unable to locate package software-properties-common"). The llvm
feature still tries to install it on demand; that's a separate fix in
the feature itself.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: chapterjason

Dockerfile.devcontainer-base

@@ -24,7 +24,6 @@ RUN apt-get update && \
         procps \
         python3 \
         rsync \
-        software-properties-common \
         strace \
         sudo \
         tar \