New upstream ffmpeg version 4.2.1 on windows

deployment/win-x86/docker-build.sh

@@ -8,7 +8,7 @@ set -o xtrace
 # Version variables
 NSSM_VERSION="nssm-2.24-101-g897c7ad"
 NSSM_URL="http://files.evilt.win/nssm/${NSSM_VERSION}.zip"
-FFMPEG_VERSION="ffmpeg-4.0.2-win32-static"
+FFMPEG_VERSION="ffmpeg-4.2.1-win32-static"
 FFMPEG_URL="https://ffmpeg.zeranoe.com/builds/win32/static/${FFMPEG_VERSION}.zip"
 
 # Move to source directory