Bump datadog_api_client to 2.28.1.dev.1 (#2093)

Co-authored-by: ci.datadog-api-spec <[email protected]>

Author: api-clients-generation-pipeline[bot]

lib/datadog_api_client/version.rb

@@ -1,5 +1,5 @@
 # Define library version.
 
 module DatadogAPIClient
-  VERSION = '2.28.1'
+  VERSION = '2.28.1.dev.1'
 end