Merge from vscode 6268feb42ba4f2e2fa15484e88c9af60d254998c (#6530)

src/vs/vscode.d.ts

@@ -4283,6 +4283,13 @@ declare module 'vscode' {
 		 * instead of fading it out.
 		 */
 		Unnecessary = 1,
+
+		/**
+		 * Deprecated or obsolete code.
+		 *
+		 * Diagnostics with this tag are rendered with a strike through.
+		 */
+		Deprecated = 2,
 	}
 
 	/**