Merge pull request #21461 from karalabe/ppa-drop-disco

build: drop disco, enable groovy on Ubuntu PPAs

build/ci.go

@@ -139,13 +139,14 @@ var (
 	// Note: zesty is unsupported because it was officially deprecated on Launchpad.
 	// Note: artful is unsupported because it was officially deprecated on Launchpad.
 	// Note: cosmic is unsupported because it was officially deprecated on Launchpad.
+	// Note: disco is unsupported because it was officially deprecated on Launchpad.
 	debDistroGoBoots = map[string]string{
 		"trusty": "golang-1.11",
 		"xenial": "golang-go",
 		"bionic": "golang-go",
-		"disco":  "golang-go",
 		"eoan":   "golang-go",
 		"focal":  "golang-go",
+		"groovy": "golang-go",
 	}
 
 	debGoBootPaths = map[string]string{