Some images embedded via <img> tags disappear after upgrading to 2.11

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Problem/Motivation

In Quickstart 2.11 all image styles were updated to convert all image types to .webp versions for better performance.
This caused all images that already existed on the site to be recreated with a .webp extension.
This also deleted all previously generated images.

If a user copied an image url that happened to be a generated image, and used it in an tag, that image is likely broken.

Example

<img alt="DVP" src="/sites/default/files/styles/thumbnail/public/2021-07/dvp-01.png">

If the image was located in a folder path starting with /sites/default/files/styles/