[ruby/irb] Bump version to 1.8.0

(https://github.com/ruby/irb/pull/700)

https://github.com/ruby/irb/commit/a061744ed3

lib/irb/version.rb

@@ -5,7 +5,7 @@
 #
 
 module IRB # :nodoc:
-  VERSION = "1.7.4"
+  VERSION = "1.8.0"
   @RELEASE_VERSION = VERSION
-  @LAST_UPDATE_DATE = "2023-07-15"
+  @LAST_UPDATE_DATE = "2023-08-30"
 end