Allow comment only for sourceswap

[eieste]

Make it Possible to comment versions only, instad of deleting them.

This should allow to set a marker for Replacements of the version via sed

Example:

@sourceswap(remote_source="git@github.com/example", version="0.0.1", local_source="../../example")
module "example" {
    source = "git@github.com/example"
    version = "0.0.1" # Comment as marker
}

If sourceswap was executed to local and back to remote the comment behind the version is lost