Do not include a backtick in error messages and backtraces (#640)

[Feature #16495]

Co-authored-by: Yusuke Endoh <mame@ruby-lang.org>

lib/reline/history.rb

@@ -62,7 +62,7 @@ def <<(val)
   private def check_index(index)
     index += size if index < 0
     if index < -2147483648 or 2147483647 < index
-      raise RangeError.new("integer #{index} too big to convert to `int'")
+      raise RangeError.new("integer #{index} too big to convert to 'int'")
     end
     # If history_size is negative, history size is unlimited.
     if @config.history_size.positive?