build: remove ubuntu 'lunar' build (#28962)

Author: holiman

build/ci.go

@@ -121,14 +121,13 @@ var (
 	// Note: vivid is unsupported because there is no golang-1.6 package for it.
 	// Note: the following Ubuntu releases have been officially deprecated on Launchpad:
 	//   wily, yakkety, zesty, artful, cosmic, disco, eoan, groovy, hirsuite, impish,
-	//   kinetic
+	//   kinetic, lunar
 	debDistroGoBoots = map[string]string{
 		"trusty": "golang-1.11", // 14.04, EOL: 04/2024
 		"xenial": "golang-go",   // 16.04, EOL: 04/2026
 		"bionic": "golang-go",   // 18.04, EOL: 04/2028
 		"focal":  "golang-go",   // 20.04, EOL: 04/2030
 		"jammy":  "golang-go",   // 22.04, EOL: 04/2032
-		"lunar":  "golang-go",   // 23.04, EOL: 01/2024
 		"mantic": "golang-go",   // 23.10, EOL: 07/2024
 	}