refactor relayer fee router tests

[liu-zhipeng]

Description

Type of change

• Docs change / dependency upgrade
• Configuration / tooling changes
• Refactoring
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Requires changes in customer code

High-level change(s) description - from the user's perspective

Related Issue(s)

Fixes

Related pull request(s)