Revert "Minor internal/reader/readability/readability.go speedup"
This reverts commit 4db138d4b8.
```
panic: runtime error: index out of range [-1]
goroutine 49 [running]:
miniflux.app/v2/internal/reader/readability.getArticle.func1(0x8?, 0xc000b56570)
/home/fred/repos/miniflux/v2/internal/reader/readability/readability.go:120 +0x2ac
github.com/PuerkitoBio/goquery.(*Selection).Each(0xc000b56510, 0xc000892fa8)
/home/fred/go/pkg/mod/github.com/!puerkito!bio/goquery@v1.9.0/iteration.go:10 +0x62
miniflux.app/v2/internal/reader/readability.getArticle(0xc00044f1f0, 0xc000a04a50)
/home/fred/repos/miniflux/v2/internal/reader/readability/readability.go:101 +0x15d
miniflux.app/v2/internal/reader/readability.ExtractContent({0x1005d00?, 0xc0001522d0?})
/home/fred/repos/miniflux/v2/internal/reader/readability/readability.go:91 +0x211
miniflux.app/v2/internal/reader/scraper.ScrapeWebsite(0xc000893688?, {0xc0007ce720, 0x54}, {0x0, 0x0})
/home/fred/repos/miniflux/v2/internal/reader/scraper/scraper.go:63 +0x859
miniflux.app/v2/internal/reader/processor.ProcessFeedEntries(0xc000133188, 0xc000502c40, 0xc0003e6360, 0x0)
/home/fred/repos/miniflux/v2/internal/reader/processor/processor.go:77 +0x8ea
miniflux.app/v2/internal/reader/handler.RefreshFeed(0xc000133188, 0x10cf, 0x52d5c, 0x0)
/home/fred/repos/miniflux/v2/internal/reader/handler/handler.go:301 +0x1485
miniflux.app/v2/internal/cli.refreshFeeds.func1(0x0)
/home/fred/repos/miniflux/v2/internal/cli/refresh_feeds.go:59 +0x2d7
created by miniflux.app/v2/internal/cli.refreshFeeds in goroutine 1
/home/fred/repos/miniflux/v2/internal/cli/refresh_feeds.go:50 +0x5d5
```
97765b93a9