[ruby/reline] Remove ARGV.first in east_asian_width.rb

(ruby/reline#587)

`ARGV.first` is the name of the EastAsianWidth file and is not needed for east_asian_width.rb

ruby/reline@6649bda31c

Author: ima1zumi

lib/reline/unicode/east_asian_width.rb

@@ -1,6 +1,5 @@
 class Reline::Unicode::EastAsianWidth
   # This is based on EastAsianWidth.txt
-  # EastAsianWidth.txt
   # UNICODE_VERSION = '15.0.0'
 
   # Fullwidth