According to qqq it's shown when info are requested for an oldid.
<https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Pageinfo-not-current/en>
Change-Id: I9c14867e216fb865d4a9109e10f3127c3c5c5a83
# Info page
'pageinfo-header' => '-', # do not translate or duplicate this message to other languages
'pageinfo-title' => 'Information for "$1"',
-'pageinfo-not-current' => 'Information may only be displayed for the current revision.',
+'pageinfo-not-current' => 'Sorry, it\'s impossible to provide this information for old revisions.',
'pageinfo-header-basic' => 'Basic information',
'pageinfo-header-edits' => 'Edit history',
'pageinfo-header-restrictions' => 'Page protection',