message: ffmpeg/3.4: update FFmpeg wrapper 2021.03
  FFmpeg 3.4.8
diff: -# Binaries branch name: ffmpeg/3.4_20200907
  -# Binaries were created for OpenCV: 03bee14372f5537daa56c62e771ec16181ca1f98
  -ocv_update(FFMPEG_BINARIES_COMMIT "2a96257b743695a47f8012aab1ffb995a1dee8b4")
  -ocv_update(FFMPEG_FILE_HASH_BIN32 "5e68a3ff82f43ac6524e50e448a34c9c")
  -ocv_update(FFMPEG_FILE_HASH_BIN64 "205db629d893e7d4865fd1459807ff47")
  +# Binaries branch name: ffmpeg/3.4_20210302
  +# Binaries were created for OpenCV: 2ab1f3f166fccc3a01497209cc01c5cea44ff201
  +ocv_update(FFMPEG_BINARIES_COMMIT "e99214251d9f3cde7c48abd46b2259bddc9885b6")
  +ocv_update(FFMPEG_FILE_HASH_BIN32 "fad5ada9be36120bba8966709e7953a8")
  +ocv_update(FFMPEG_FILE_HASH_BIN64 "650e2272728491923e566f784f79cfef")
  ocv_update(FFMPEG_FILE_HASH_CMAKE "3b90f67f4b429e77d3da36698cef700c")
  function(download_win_ffmpeg script_var)
  