validators: Remove undefined where only string value expected

[regexowl]

This removes checks for an undefined value in validators that take only string.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.85%. Comparing base (f5fa3d7) to head (e04616d).

@@            Coverage Diff             @@
##             main    #2754      +/-   ##
==========================================
- Coverage   84.86%   84.85%   -0.01%     
==========================================
  Files         184      184              
  Lines       20827    20818       -9     
  Branches     2022     2022              
==========================================
- Hits        17675    17666       -9     
  Misses       3130     3130              
  Partials       22       22              

Files with missing lines	Coverage Δ
src/Components/CreateImageWizard/validators.ts	93.15% <100.00%> (-0.76%)	⬇️

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