Billing_plan field deprecation - correction start date (DataDog#3059)

Co-authored-by: ci.datadog-api-spec <packages@datadoghq.com>

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

.generator/schemas/v1/openapi.yaml

@@ -20236,7 +20236,7 @@ components:
           type: string
         billing_plan:
           deprecated: true
-          description: The billing plan (metadata). (Deprecated from May 2026)
+          description: The billing plan (metadata). (Deprecated from June 2026)
           type: string
         end_date:
           description: Shows the last date of usage.

lib/datadog_api_client/v1/models/usage_billable_summary_hour.rb

@@ -27,7 +27,7 @@ class UsageBillableSummaryHour
     # The account public ID.
     attr_accessor :account_public_id
 
-    # The billing plan (metadata). (Deprecated from May 2026)
+    # The billing plan (metadata). (Deprecated from June 2026)
     attr_accessor :billing_plan
 
     # Shows the last date of usage.