executors/PAS: drop -So argument

[Xyene]

This was inherited from PEG, but doesn't seem to be specified by other
online judges.

-So
    Try to be Borland TP 7.0 compatible (no function overloading etc.).

[codecov-commenter]

Codecov Report

Merging #959 (766b7bf) into master (08e69d7) will decrease coverage by 0.12%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #959      +/-   ##
==========================================
- Coverage   86.54%   86.42%   -0.13%     
==========================================
  Files         138      138              
  Lines        4735     4735              
==========================================
- Hits         4098     4092       -6     
- Misses        637      643       +6     

Impacted Files	Coverage Δ
dmoj/executors/PAS.py	100.00% <100.00%> (ø)
dmoj/cptbox/tracer.py	83.27% <0.00%> (-1.82%)	⬇️
dmoj/result.py	89.33% <0.00%> (-1.34%)	⬇️

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