lint/format - remove superfluous newlines from end of test-*.log files

[andrewkroh]

Empty lines at the end of test log files are easy to accidentally add and hard to spot. They get read during test cases and make their way into expected data files. It would be nice if the format command could trim those files and lint could notify the developer about them.

Here's an example:

https://github.com/elastic/integrations/blob/b657f1c651e95fad4d9de584866cd0f0ce7cf17a/packages/aws/data_stream/cloudtrail/_dev/test/pipeline/test-update-user-json.log#L2

https://github.com/elastic/integrations/blob/b657f1c651e95fad4d9de584866cd0f0ce7cf17a/packages/aws/data_stream/cloudtrail/_dev/test/pipeline/test-update-user-json.log-expected.json#L83-L96