fix inconsistency in metadata yaml key name

video_frame should have been video_frame_file

poses_files_metadata.yaml

@@ -152,7 +152,7 @@
   shared_by:
     name: "Laura Schwarz"
     affiliation: "Sainsbury Wellcome Centre, UCL"
-  video_frame: null
+  video_frame_file: null
   note: "The tracks have not been fully corrected, they still contain identity switches. This file does NOT correspond to the .slp file with the same prefix."
 
 - file_name: "SLEAP_two-mice_social-interaction.predictions.slp"