Media: skip server image support check when using client-side media.

When uploading images via the REST API with `generate_sub_sizes` set to `false`, skip server support checks since processing is handled on the client side. Fix an issue where uploads of formats like AVIF fail with `rest_upload_image_type_not_supported`, even though the client will  handle all image processing and the server doesn't need to support the format.

See also https://github.com/WordPress/gutenberg/issues/76369 and https://github.com/WordPress/gutenberg/pull/76371.

Props adamsilverstein, westonruter, andrewserong, mukesh27.
Fixes #64836. See #62717.



git-svn-id: https://develop.svn.wordpress.org/trunk@61980 602fd350-edb4-49c9-b593-d223f7449a82