added java sdk generation for reservations api (Microsoft.Capacity) (#20130)

Author: dennis-menge

specification/reservations/resource-manager/readme.md

@@ -136,6 +136,7 @@ swagger-to-sdk:
   - repo: azure-cli-extensions
   - repo: azure-resource-manager-schemas
   - repo: azure-powershell
+  - repo: azure-sdk-for-java
 ```
 
 ## C#