[chore]: enable error-nil rule from testifylint

[mmorel-35]

Description

Testifylint is a linter that provides best practices with the use of testify.

This PR enables error-nil rule from testifylint

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.5%. Comparing base (316114c) to head (d26b5c0).
Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #5843   +/-   ##
=====================================
  Coverage   84.5%   84.5%           
=====================================
  Files        272     272           
  Lines      22734   22734           
=====================================
+ Hits       19225   19228    +3     
+ Misses      3166    3163    -3     
  Partials     343     343           

see 2 files with indirect coverage changes