chore(samples): add sample for spanner editions

[rahul2393]

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:

• Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
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Fixes #<issue_number_goes_here> ☕️

If you write sample code, please follow the samples format.

[snippet-bot]

Here is the summary of changes.

You are about to add 2 region tags.

• samples/snippets/src/main/java/com/example/spanner/CreateInstanceExample.java:19, tag spanner_create_instance
• samples/snippets/src/main/java/com/example/spanner/UpdateInstanceExample.java:19, tag spanner_update_instance

You are about to delete 1 region tag.

• samples/snippets/src/main/java/com/example/spanner/CreateInstanceExample.java:19, tag spanner_create_instance

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[nithinsujir]

Edition sample change lgtm. (There are other unrelated changes which I've not reviewed)

[rahul2393]

Other changes are mostly related to running mvn:format