External Libraries: Update Jcrop to version 0.9.15.
For a full list of changes, see https://github.com/tapmodo/Jcrop/compare/v0.9.12...v0.9.15.
This change also adds a comment in `script-loader.php` indicating that this library is no longer used by core.
Follow-up to [10846], [10863], [11015], [21633], [25549].
Props hareesh-pillai, karpstrucking, SergeyBiryukov.
Fixes #54035.
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git-svn-id: http://core.svn.wordpress.org/trunk@52578 1a063a9b-81f0-0310-95a4-ce76da25c4cd