Fix Image constraint class and validator link

Change Image constraint links from File and FileValidator to Image and ImageValidator.
bug #3747 Fix Image constraint class and validator link (weaverryan)

This PR was merged into the 2.3 branch.

Discussion
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Fix Image constraint class and validator link

Just a rebase of #3646...

Commits
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2a3955b Fix Image constraint class and validator link
Merge branch '2.3' into 2.4