Don't pin relayer tag to "main"

[chatton]

Summary of Bug

Currently we pin relayer tag to "main" this can lead to tests all of a sudden failing if a bad change is merged to main in the go relayer repo.

Expected Behaviour

We should pin a stable version and be able to update it easily.

Version

Steps to Reproduce

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For Admin Use

• Not duplicate issue
• Appropriate labels applied
• Appropriate contributors tagged/assigned