Since kernel 7.0 translateVersion method was removed from the ContentService interface:
https://github.com/ezsystems/ezpublish-kernel/commit/ccc80ae4a327c11c5ce0eac66a54d0bdc6bdd00f#diff-4321ba086690f6f89abef111ea256618L256

but SignalSlot\ContentService still relates to it:
https://github.com/ezsystems/ezpublish-kernel/blob/7.5/eZ/Publish/Core/SignalSlot/ContentService.php#L383