If You track down the link to the image itself, You get ttps://camo.githubusercontent.com/e3e0a24d2265728072d9e65220a41d2ddd6b42bb/68747470733a2f2f7773322e73696e61696d672e636e2f6c617267652f303036744b6654636779316731326132653362306a6a3331666c3062683433312e6a7067 which returns "bad signature"
Basically the title - the images in docs have either been moved or their permissions have been changed, e.g. https://github.com/doccano/doccano/blob/master/docs/advanced/aws_https_settings.md
If You track down the link to the image itself, You get ttps://camo.githubusercontent.com/e3e0a24d2265728072d9e65220a41d2ddd6b42bb/68747470733a2f2f7773322e73696e61696d672e636e2f6c617267652f303036744b6654636779316731326132653362306a6a3331666c3062683433312e6a7067 which returns "bad signature"