Use TxSigLimit instead of default constant value

[alexanderbez]

closes: #4394

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[codecov]

Codecov Report

Merging #4396 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #4396      +/-   ##
==========================================
+ Coverage   57.21%   57.24%   +0.02%     
==========================================
  Files         241      241              
  Lines       15126    15131       +5     
==========================================
+ Hits         8654     8661       +7     
+ Misses       5842     5840       -2     
  Partials      630      630

[rigelrozanski]

Yup this makes sense - so we've moved the sig check logic from ValidateBasic (on stdTx) to a new check directly above this within NewAnteHandler. Got it looks, good.