Fix go install installation

[elopez]

$ go install github.com/crytic/medusa@latest
go: github.com/crytic/medusa@latest (in github.com/crytic/[email protected]):
	The go.mod file for the module providing named packages contains one or
	more replace directives. It must not contain directives that would cause
	it to be interpreted differently than if it were the main module.

This is caused by a leftover replace in go.mod. Medusa no longer references github.com/ethereum/go-ethereum so it should be ok to remove.

[anishnaik]

FFFFFFFFFFFF how did I miss this