Update default gems list at 509f04ca91 [ci skip]

NEWS.md

@@ -253,7 +253,7 @@ Note: We're only listing outstanding class updates.
     * io-nonblock 0.1.1
     * io-wait 0.3.0.pre
     * ipaddr 1.2.4
-    * irb 1.4.3
+    * irb 1.5.0
     * json 2.6.2
     * logger 1.5.1
     * net-http 0.3.0