fix: updating error page
the caption is updated to CC BY 2.0
[Phabicator T218898]
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- <a href="https://flic.kr/p/UHr11n">Say what?</a> by <a href="https://www.flickr.com/photos/armydre2008/">frankieleon</a>, on Flickr; CC BY
+ <a href="https://flic.kr/p/UHr11n">Say what?</a> by <a href="https://www.flickr.com/photos/armydre2008/">frankieleon</a>, on Flickr; CC BY 2.0
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