Fix invalid escape sequence

[njzjz]

Fix the following warnings: DeprecationWarning: invalid escape sequence

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.01% ⚠️

Comparison is base (7da9aaf) 75.52% compared to head (642a522) 75.51%.

Additional details and impacted files

@@            Coverage Diff             @@
##            devel    #2820      +/-   ##
==========================================
- Coverage   75.52%   75.51%   -0.01%     
==========================================
  Files         242      242              
  Lines       24162    24162              
  Branches     1533     1533              
==========================================
- Hits        18249    18247       -2     
  Misses       4997     4997              
- Partials      916      918       +2     

Files Changed	Coverage Δ
deepmd/utils/argcheck.py	96.05% <100.00%> (ø)
deepmd/utils/convert.py	70.44% <100.00%> (ø)

... and 1 file with indirect coverage changes

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