Update benchmark weight

[HenriqueNogara]

Updates the weight function for the contract benchmark.

changelog

[codecov[bot]]

Codecov Report

Merging #1524 (2469547) into develop (43f4010) will decrease coverage by 0.04%. The diff coverage is 0.00%.

@@             Coverage Diff             @@
##           develop    #1524      +/-   ##
===========================================
- Coverage    58.51%   58.47%   -0.04%     
===========================================
  Files          142      142              
  Lines        31413    31414       +1     
===========================================
- Hits         18380    18370      -10     
- Misses       13033    13044      +11     

Files Changed	Coverage Δ
pallets/weights/src/polymesh_contracts.rs	25.00% <0.00%> (-0.22%)	:arrow_down:

... and 4 files with indirect coverage changes