correct the sthv1/sthv2 rawframes filelist generate command

[yzfly]

tools/data/build_file_list.py only support two format ['rawframes', 'videos'], add missing 's' for the sthv1/sthv2 rawframes filelist generate command.
parser.add_argument( '--format', type=str, default='rawframes', choices=['rawframes', 'videos'], help='data format')

[codecov]

Codecov Report

Merging #71 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #71   +/-   ##
=======================================
  Coverage   85.22%   85.22%           
=======================================
  Files          73       73           
  Lines        3994     3994           
  Branches      645      645           
=======================================
  Hits         3404     3404           
  Misses        485      485           
  Partials      105      105           

Flag	Coverage Δ
#unittests	85.22% <ø> (ø)

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[innerlee]

thanks!