Export tests: say why the H.264 pin moved with FilmCraft 09aaf9b (#1701)

crates/export/tests/it/movie_bytes.rs

@@ -94,6 +94,8 @@ fn export_bytes(format: OutputFormat, name: &str) -> Vec<u8> {
 #[test]
 fn h264_movie_bytes_are_pinned() {
     let data = export_bytes(OutputFormat::H264, "/out/pinned.mp4");
+    // FilmCraft 09aaf9b's encoder lists its settings in the first frame's user-data SEI (211
+    // bytes where 0.1.1's name took 50): 161 bytes more than the FilmCraft 2c5ba7a pin.
     assert_eq!((data.len(), fnv1a(&data)), (104_341, 17_655_680_090_264_218_914), "H.264 MP4");
 }