Remove docker prereqs scripts that only install a package. Add informational message for this. (#14661)

virtualization/Docker/scripts/ffmpeg

@@ -1,11 +0,0 @@
-#!/bin/bash
-# Sets up ffmpeg.
-
-# Stop on errors
-set -e
-
-PACKAGES=(
-  ffmpeg
-)
-
-apt-get install -y --no-install-recommends ${PACKAGES[@]}

virtualization/Docker/scripts/iperf3

@@ -1,11 +0,0 @@
-#!/bin/bash
-# Sets up iperf3.
-
-# Stop on errors
-set -e
-
-PACKAGES=(
-  iperf3
-)
-
-apt-get install -y --no-install-recommends ${PACKAGES[@]}