Makefile: clean up existing "bridge" directories

... which were renamed to "node".

Change-Id: I092e76a70b2762b0c18a82e4c8f1816c207be105

Makefile

@@ -23,6 +23,7 @@ install:
 .PHONY: generate
 generate: dirs
 	cd tools && ./build.sh
+	rm -rf bridge
 	rm -rf node/pkg/proto
 	tools/bin/buf generate