samples: region tag pubsub_publisher_with_compression

[anguillanneuf]

Forgot to add region tag in #1131

[snippet-bot]

Here is the summary of changes.

You are about to add 1 region tag.

• samples/snippets/src/main/java/pubsub/PublishWithGrpcCompressionExample.java:19, tag pubsub_publisher_with_compression

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