vendor: update git url handling with changes to buildkit

The git ssh url parsing API changed a bit and broke how buildx utilized
the API. This updates the affected method with the new method of
identifying an SSH url.

Signed-off-by: Jonathan A. Sternberg <jonathan.sternberg@docker.com>

vendor/github.com/moby/buildkit/util/progress/multiwriter.go

@@ -65,7 +65,7 @@ func (ps *MultiWriter) Write(id string, v interface{}) error {
 		Sys:       v,
 		meta:      ps.meta,
 	}
-	return ps.WriteRawProgress(p)
+	return ps.writeRawProgress(p)
 }
 
 func (ps *MultiWriter) WriteRawProgress(p *Progress) error {