Undocumented checks prevent PublishEventRequest metadata fields to reach the pubsub.azure.servicebus component

## Expected Behavior

When we set metadata fields on a [PublishEventRequest](https://github.com/dapr/java-sdk/blob/master/sdk/src/main/java/io/dapr/client/domain/PublishEventRequest.java) field, they should be received and processed by the pubsub.azure.servicebus component.

## Actual Behavior

It seems like the fields are set properly (when we log the PublishEventRequest object before publishing it we can see them), but they do not reach the component (visible when inspecting the events in the Azure Portal).

## Steps to Reproduce the Problem

Tested with dapr-sdk version 1.3.1 and dapr-runtime 1.4.3

1. Create a PublishEventRequest
2. Set a metadata field, e.g., with `eventRequest.getMetadata().put(“MessageId”, id);` and `eventRequest.getMetadata().put(“ScheduledEnqueueTimeUtc”, “Wed Jan 19 11:06:00 GMT 2022”)`
3. Log the PublishEventRequest, the output might look like so: `publishing event with metadata: ScheduledEnqueueTimeUtc=Wed Jan 19 11:06:00 GMT 2022;MessageId=time-trigger;1642590360;Europe/Berlin;0;1000`
4. Publish the event via Dapr
5. Observe the event in the Azure portal, the events do not have a message id and are also available immediately.

## Release Note

RELEASE NOTE: