fix: Use gmp module account as relayer address in handler

[rbajollari]

Description

closes: #XXXX

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Author Checklist

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[codecov-commenter]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (5cc3e92) 16.10% compared to head (dc6ce4d) 16.10%.

Files	Patch %	Lines
app/gmpmiddleware/handler.go	0.00%	6 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #344      +/-   ##
==========================================
- Coverage   16.10%   16.10%   -0.01%     
==========================================
  Files          78       78              
  Lines       18765    18769       +4     
==========================================
  Hits         3022     3022              
- Misses      15590    15594       +4     
  Partials      153      153              

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[adamewozniak]

one comment, but aside from that lgtm!