Update default gems list at ad8cb53 [ci skip]

Author: matzbot

NEWS.md

@@ -58,6 +58,7 @@ The following default gems are updated.
 * prism 1.4.0
 * psych 5.2.3
 * stringio 3.1.6
+* strscan 3.1.3
 * uri 1.0.3
 
 The following bundled gems are added.