Remove --skip-kati

Not used anymore.

Test: No
Change-Id: Ide0d29b773583d6a8faff5b41a82d650cc2f9bcb

ui/build/config.go

@@ -813,9 +813,6 @@ func (c *configImpl) parseArgs(ctx Context, args []string) {
 			//   by a previous build.
 			c.skipConfig = true
 			c.skipKati = true
-		} else if arg == "--skip-kati" {
-			// TODO: remove --skip-kati once module builds have been migrated to --song-only
-			c.skipKati = true
 		} else if arg == "--soong-only" {
 			c.skipKati = true
 			c.skipKatiNinja = true