Add unique week check in formatNumericWeeks

[jloh02]

Context

#3648

Implementation

TimetableCell
formatNumericWeeks does a check to ensure listed weeks are unique. Also update condition for change in week <= 1 instead

Other Information

Instead of simply ensuring unique, should we also sort the weeks and maintain the <= 1 condition?

[vercel]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 53.62%. Comparing base (711a6da) to head (eba7f1b).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3677      +/-   ##
==========================================
+ Coverage   53.60%   53.62%   +0.01%     
==========================================
  Files         272      272              
  Lines        5977     5979       +2     
  Branches     1428     1428              
==========================================
+ Hits         3204     3206       +2     
  Misses       2773     2773              

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[kokrui]

LGTM! I'll create a new issue to add warnings in our scraper (so we notice these sorts of incorrectly-entered data if we want to let the departments know)