rm bin/generate-chapters-length

it was a one-off script.. with "bindata/chapters-length.json" in the
repository we don't need it anymore.

bin/generate-chapters-length

@@ -1,16 +0,0 @@
-#!/usr/bin/env ruby
-
-##
-# This script generates bindata/chapters-length.json - a JSON file
-# that maps each chapter in The Qur'an to the number of verses
-# a chapter contains.
-
-require "json"
-src = File.join("src", "json", "ar", "%{chapter}.json")
-result = {}
-1.upto(114) do
-  path = format(src, chapter: _1)
-  result[_1] = JSON.parse(File.read(path)).size
-end
-File.write File.join("bindata", "chapters-length.json"),
-           JSON.pretty_generate(result)