Update default gems list at f102901 [ci skip]

Author: matzbot

NEWS.md

@@ -96,7 +96,7 @@ The following default gems are updated.
 * optparse 0.5.0
 * pathname 0.4.0
 * prism 1.0.0
-* psych 5.2.0.beta1
+* psych 5.2.0.beta2
 * rdoc 6.7.0
 * reline 0.5.10
 * resolv 0.4.0