fix: enforce camera info to be extracted from video itself instead of gpx

[ptpt]

Problem is when run:

mapillary_tools process --video_geotag_source '{"source":"gpx","pattern":"/external_gpx/%g.gpx"}' ~/Downloads/video\ full.360

will throw this exception (warning) and skip gpx geotagging:

Exception for parser gpx while processing source /external_gpx/video full.gpx: "unable find box at path [b'moov']"