Update default gems list at c51668d [ci skip]

Author: matzbot

NEWS.md

@@ -38,7 +38,6 @@ The following default gems are updated.
 * RubyGems 3.7.0.dev
 * bundler 2.7.0.dev
 * fiddle 1.1.7.dev
-* irb 1.15.1
 * prism 1.3.0
 * psych 5.2.3
 * stringio 3.1.3.dev