Add a missing require to the bump-version script

Author: elia

bin/release/bump-version

@@ -1,6 +1,7 @@
 #!/usr/bin/env ruby
 # frozen_string_literal: true
 
+require_relative '_helpers'
 require_relative '../../core/lib/spree/core/version'
 
 path = "#{ROOT}/core/lib/spree/core/version.rb"