Renamed data prepper files to have dashes for consistency

[kolchfa-aws]

The convention for our documentation site is to use dashes instead of underscores in file names. File names determine links on the website, and dashes are preferable for readability and SEO.

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[kolchfa-aws]

@dlvenable Could you review this PR? I hope our file naming convention works for the data prepper team.

[hdhalter]

Underscores in the file names are required by the auto-generation initiative. @dlvenable - is there a workaround to changing the file names?