release: remove "depends" dependency

* the new "dep ensure" step can modify the working tree,
  which breaks the release process.

Author: Alex Buchanan

Makefile

@@ -191,7 +191,7 @@ snapshot: depends
 		--rm-dist \
 		--snapshot
 
-release: depends
+release:
 	@go get github.com/buchanae/github-release-notes
 	@goreleaser \
 		--rm-dist \