[Java] UI to add EventGridSubscription is disabled

Repro:
- [Create new Java Function using mvn]( https://docs.microsoft.com/en-us/azure/azure-functions/functions-create-first-java-maven#generate-a-new-functions-project)

- Add EventHubTrigger in function.java
```
@FunctionName("EventGridTestJava")
public void EventGridTestJava(
@EventGridTrigger(name = "eventgrid") String message, final ExecutionContext context) {
context.getLogger().info("Java Event Grid trigger function executed.");
context.getLogger().info(message);
}
```
-[ Publish Java function with EventGridTrigger using maven](https://docs.microsoft.com/en-us/azure/azure-functions/functions-create-first-java-maven#deploy-the-function-to-azure)

UI to add EventGridSubscription is disabled

Workaround:
Add C# EventGridTrigger. UI works as expected after installing EventGridExtension