fixed the computed fee for outport for relayed v3

[sstanculeanu]

Reasoning behind the pull request

• the fee fomr indexer was not the correct one

Proposed changes

• outport fee handling needs special treatment for relayed v3, similar as for transaction api of the node

Testing procedure

• with feat branch, comparison between gateway and explorer/api results

Pre-requisites

Based on the Contributing Guidelines the PR author and the reviewers must check the following requirements are met:

• was the PR targeted to the correct branch?
• if this is a larger feature that probably needs more than one PR, is there a feat branch created?
• if this is a feat branch merging, do all satellite projects have a proper tag inside go.mod?