[ruby/irb] Bump version to 1.6.3

(https://github.com/ruby/irb/pull/537)

https://github.com/ruby/irb/commit/110e4a3219

lib/irb/version.rb

@@ -5,7 +5,7 @@
 #
 
 module IRB # :nodoc:
-  VERSION = "1.6.2"
+  VERSION = "1.6.3"
   @RELEASE_VERSION = VERSION
-  @LAST_UPDATE_DATE = "2022-12-13"
+  @LAST_UPDATE_DATE = "2023-03-06"
 end