breakfix: sparse trait missing on support service (#2050)

Sync models and regenerate to pickup missing sparse trait. This is a breakfix change to properly support the following operations: * `DescribeTrustedAdvisorCheckRefreshStatuses` * `DescribeTrustedAdvisorCheckSummaries` ticket: P83022241

Author: aajtodd

.changelog/0f5dd0f8fd8b49f88e6e94695a9221ad.json

@@ -0,0 +1,8 @@
+{
+ "id": "0f5dd0f8-fd8b-49f8-8e6e-94695a9221ad",
+ "type": "announcement",
+ "description": "Model regenerated with support for null string values to properly implement `support` service operations `DescribeTrustedAdvisorCheckRefreshStatuses` and `DescribeTrustedAdvisorCheckSummaries`",
+ "modules": [
+ "service/support"
+ ]
+}