fate/ffm: Update test ref

Since timecode_frame)start is a private option now, it stays at the default,
and is no longer written to the file.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>

tests/ref/lavf/ffm

@@ -1,3 +1,3 @@
-6abbc926535ef17bdbc0e847249d4cee *./tests/data/lavf/lavf.ffm
+e63c16b5f0ad5015304fc4009fdb33ca *./tests/data/lavf/lavf.ffm
 376832 ./tests/data/lavf/lavf.ffm
 ./tests/data/lavf/lavf.ffm CRC=0x000e23ae