Remove replace directives from go.mod

[0pcom]

it's possible to go run ... skywire services without cloning the repo ; however this does not work for skywire with the replace directives in go.mod of this repo.

go run github.com/skycoin/skywire/cmd/skycoin-skywire@develop
go: github.com/skycoin/skywire/cmd/skycoin-skywire@develop (in github.com/skycoin/[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 PR removes those replace directives