Return a failed future on deadline expiration

[kunalrkak]

Before this PR

From the Channel Javadoc:

Behavior

Implementations of {@link Channel#execute(Endpoint, Request)} must never throw. A failed {@link ListenableFuture} must be returned instead.

The DeadlineExpiredException is logged when we handle throwables here, so we should just be able to return a failed future.

After this PR

==COMMIT_MSG==
Makes DeadlineAdvertisementChannel adhere to the Channel spec by not throwing an exception.
==COMMIT_MSG==

Possible downsides?

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Description

Makes DeadlineAdvertisementChannel adhere to the Channel spec by not throwing an exception.

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Invalidated by push of 3e85783

[autorelease3]

Released 6.2.0