BF: if PsychoPy version includes "postN" then strip from PsychoJS version number

[peircej]

Originally we only expected to use rcN, aN, bN, devN tags but recently we used postN which broke the PsychoJS experiments

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 49.62%. Comparing base (eb5e61b) to head (ba940ca).
Report is 26 commits behind head on release.

Additional details and impacted files

@@             Coverage Diff             @@
##           release    #6873      +/-   ##
===========================================
- Coverage    49.64%   49.62%   -0.02%     
===========================================
  Files          332      332              
  Lines        61204    61206       +2     
===========================================
- Hits         30383    30372      -11     
- Misses       30821    30834      +13     

Components	Coverage Δ
app	∅ <ø> (∅)
boilerplate	∅ <ø> (∅)
library	∅ <ø> (∅)
vm-safe library	∅ <ø> (∅)

[JartanFTW]

👍 PR looks good to me. Very little code to check 😛