mgmt, managednetworkfabric, update java option (#24569)

Author: weidongxu-microsoft

specification/managednetworkfabric/resource-manager/readme.java.md

@@ -0,0 +1,7 @@
+## Java
+
+These settings apply only when `--java` is specified on the command line.
+
+```yaml $(java)
+service-name: Managed Network Fabric
+```

specification/managednetworkfabric/resource-manager/readme.md

@@ -84,11 +84,14 @@ See configuration in [readme.go.md](./readme.go.md)
 
 See configuration in [readme.python.md](./readme.python.md)
 
-
 ## TypeScript
 
 See configuration in [readme.typescript.md](./readme.typescript.md)
 
 ## CSharp
 
 See configuration in [readme.csharp.md](./readme.csharp.md)
+
+## Java
+
+See configuration in [readme.java.md](./readme.java.md)