[mod] container: remove `Cache-Control` header (#5005)

Granian shouldn't actually handle the cache, we leave that to the upstream proxy.

Related https://github.com/searxng/searxng/pull/5004

container/Dockerfile

@@ -52,8 +52,7 @@ ENV SEARXNG_VERSION="$SEARXNG_GIT_VERSION" \
     GRANIAN_BLOCKING_THREADS="4" \
     GRANIAN_WORKERS_KILL_TIMEOUT="30" \
     GRANIAN_BLOCKING_THREADS_IDLE_TIMEOUT="300" \
-    GRANIAN_STATIC_PATH_MOUNT="/usr/local/searxng/searx/static/" \
-    GRANIAN_STATIC_PATH_EXPIRES="3600"
+    GRANIAN_STATIC_PATH_MOUNT="/usr/local/searxng/searx/static/"
 
 VOLUME $CONFIG_PATH
 VOLUME $DATA_PATH