delete dump.0.xyz in back_forward file

[fqgong]

No description provided.

[codecov-commenter]

Codecov Report

Merging #498 (722944e) into devel (1c18b1c) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##            devel     #498   +/-   ##
=======================================
  Coverage   33.02%   33.02%           
=======================================
  Files          86       86           
  Lines       14675    14675           
=======================================
  Hits         4847     4847           
  Misses       9828     9828           

Impacted Files	Coverage Δ
dpgen/generator/run.py	66.26% <0.00%> (ø)

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