Add missing break statement

[masafm]

What does this PR do?

Break statement will be executed when flush() succeeds.

Motivation

Without break statement lambda function will submit the same metrics 5 times in a row.

Testing Guidelines

I tested this by deploying to my lambda function.

Before fix: metrics are submitted 5 times.

2024-02-08T10:06:49.242+09:00	START RequestId: a98d2fbb-d93b-4cd8-a627-c0a816d72ba0 Version: $LATEST
2024-02-08T10:06:50.491+09:00	INFO Submitted data with status: 202
2024-02-08T10:06:51.733+09:00	INFO Submitted data with status: 202
2024-02-08T10:06:52.980+09:00	INFO Submitted data with status: 202
2024-02-08T10:06:54.216+09:00	INFO Submitted data with status: 202
2024-02-08T10:06:55.454+09:00	INFO Submitted data with status: 202
2024-02-08T10:06:55.475+09:00	END RequestId: a98d2fbb-d93b-4cd8-a627-c0a816d72ba0

After fix: metrics are submitted only once.

2024-02-08T10:22:08.831+09:00	START RequestId: 1541446c-d918-48c7-869f-41232832c8eb Version: $LATEST
2024-02-08T10:22:10.329+09:00	INFO Submitted data with status: 202
2024-02-08T10:22:10.352+09:00	END RequestId: 1541446c-d918-48c7-869f-41232832c8eb

Additional Notes

Types of changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

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• This PR contains breaking changes that are documented in the description
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