Update OpenSearch LicenseHeaders to use the short version

[peterzhuamazon]

Signed-off-by: Peter Zhu zhujiaxi@amazon.com

Description

Update OpenSearch LicenseHeaders to use the short version.

• It removes the Amazon related info and change to OpenSearch Contributors for copyrights.
• It also changed to a short version which is cleaner and still has enough information.

Issues Resolved

#21

Check List

• Commits are signed per the DCO using --signoff

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[dblock]

Is the short version the preferred version, @hyandell?

[hyandell]

Yes, that's the preferred version.

In the text however, I would say this:

New files in your code contributions should contain the following license header. If you are modifying existing files with license headers, or including new files that already have license headers, do not remove or modify them without guidance.

[peterzhuamazon]

@hyandell Please check again I updated the text based on your suggestions.

[peterzhuamazon]

Thanks @hyandell for approval @dblock please merge it. Thanks.