fix(axelar-gateway): ensure the testutils feature is loaded for tests

[cgorenflo]

the tests import structs from the testutils module, which is only loaded when the testutils feature is active. So the test should ensure that it is

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.16%. Comparing base (3bfc691) to head (eac676f).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #70   +/-   ##
=======================================
  Coverage   93.16%   93.16%           
=======================================
  Files          36       36           
  Lines        2267     2267           
=======================================
  Hits         2112     2112           
  Misses        155      155           

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