gallery-dl: Update to 1.16.0

Changes:
1.16.0
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### Additions
- [booru] implement generalized extractors for `*booru` and `moebooru` sites
  - add support for sakugabooru.com (#1136)
  - add support for lolibooru.moe (#1050)
  - provide formattable `date` metadata fields (#1138)
- [postprocessor:metadata] add `event` and `filename` options (#315, #866, #984)
- [postprocessor:exec] add `event` option (#992)

### Changes
- [flickr] update default directories and improve metadata consistency (#828)
- [sankaku] use API endpoints from `beta.sankakucomplex.com`
- [downloader:http] improve filename extension handling (#776)
- replace all JPEG filename extensions with `jpg` by default

### Fixes
- [hentainexus] fix extraction (#1166)
- [instagram] rewrite (#1113, #1122, #1128, #1130, #1149)
- [mangadex] handle external chapters (#1154)
- [nozomi] handle empty `date` fields  (#1163)
- [paheal] create directory for each post (#1147)
- [piczel] update API URLs
- [twitter] update image URL format (#1145)
- [twitter] improve `x-csrf-token` header handling (#1170)
- [webtoons] update `ageGate` cookies

### Removals
- [sankaku] remove login support

(leot)