bugfix: Fix Game.String() variations output

[mikeb26]

After a variation has been output, the move number should always be repeated.

[codecov]

Codecov Report

Attention: Patch coverage is 94.11765% with 2 lines in your changes missing coverage. Please review.

Project coverage is 66.75%. Comparing base (949320f) to head (f3405a5).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
game.go	93.54%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #55      +/-   ##
==========================================
+ Coverage   66.52%   66.75%   +0.22%     
==========================================
  Files          27       27              
  Lines        4675     4692      +17     
==========================================
+ Hits         3110     3132      +22     
+ Misses       1441     1436       -5     
  Partials      124      124              

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