build: reset the version suffix cadence to 'nil'

Updated the `version.rb` `SUFFIX` entry to be `nil` by default to ensure the version number is correctly formatted.

lib/data_services_api/version.rb

@@ -5,6 +5,6 @@ module DataServicesApi
   MAJOR = 1
   MINOR = 5
   PATCH = 1
-  SUFFIX = 0
+  SUFFIX = nil
   VERSION = "#{MAJOR}.#{MINOR}.#{PATCH}#{SUFFIX && ".#{SUFFIX}"}"
 end