If Carousel is enabled, Jetpack adds data attributes to page and post images, regardless of whether or not the images are part of a Carousel Gallery. I have replicated the issue using Twenty Seventeen 1.3 and Jetpack 5.3.

As per @jeherve, this appears to be a bug.
3255391-t
Also reported here:
https://wordpress.org/support/topic/carousel-meta-information-removal/
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Also reported here:
https://wordpress.org/support/topic/carousel-meta-information-removal/