Delete app cache according to hadolint

Otherwise we have an extra 100s of MBs of stale cache

Dockerfile.debian-bookworm-hugo

@@ -5,5 +5,6 @@ ENV DEBIAN_FRONTEND=noninteractive
 RUN apt-get -qq update && \
     apt-get -qq upgrade && \
     apt-get -qq install hugo && \
-    apt-get -qq clean
-RUN hugo version
+    apt-get -qq clean && \
+    rm -rf /var/lib/apt/lists/* && \
+    hugo version

Dockerfile.debian-trixie-hugo

@@ -5,4 +5,5 @@ ENV DEBIAN_FRONTEND=noninteractive
 RUN apt-get -qq update && \
     apt-get -qq upgrade && \
     apt-get -qq install hugo && \
-    apt-get -qq clean
+    apt-get -qq clean && \
+    rm -rf /var/lib/apt/lists/*