Academy tutorials reference external image URLs instead of local assets

[katzino]

reported via slack

Four Academy tutorial pages pull images from https://raw.githubusercontent.com/apify/actor-scraper/master/docs/img/*.webp instead of the local assets at sources/academy/tutorials/apify_scrapers/images/*.jpg. Two referenced filenames (modified-date.webp, task-name.webp) have no local equivalent. All images also use ![$1] as alt text.

Example URL: https://docs.apify.com/academy/apify-scrapers/cheerio-scraper