remove jingo (#3506)

- unmaintained since Jan, 2021
- unaddressed security issues
- ref. https://github.com/awesome-selfhosted/awesome-selfhosted/issues/3499

README.md

@@ -2074,7 +2074,6 @@ _See also: [Wikimatrix](https://www.wikimatrix.org/), [Wiki Engines - WikiIndex]
 - [Gitit](https://github.com/jgm/gitit) - Wiki program that stores pages and uploaded files in a git repository, which can then be modified using the VCS command line tools or the wiki's web interface. `GPL-2.0` `Haskell`
 - [Gollum](https://github.com/gollum/gollum) - Simple, Git-powered wiki with a sweet API and local frontend. `MIT` `Ruby`
 - [Instiki](https://golem.ph.utexas.edu/wiki/instiki/show/HomePage) - Instiki is a wiki clone so pretty and easy to set up, you'll wonder if it’s really a wiki. Runs on Rails and focuses on portability and stability. ([Source Code](https://github.com/parasew/instiki)) `Ruby` `Ruby`
-- [jingo](https://github.com/claudioc/jingo) - Git based wiki engine written for node.js, with a decent design, a search capability and good typography. `MIT` `Nodejs`
 - [Mediawiki](https://www.mediawiki.org/wiki/MediaWiki) - MediaWiki is a free and open-source wiki software package written in PHP. It serves as the platform for Wikipedia and the other Wikimedia projects, used by hundreds of millions of people each month. ([Demo](https://en.wikipedia.org/wiki/Main_Page), [Source Code](https://phabricator.wikimedia.org/diffusion/MW/)) `GPL-2.0` `PHP`
 - [Outline](https://www.getoutline.com/) `⚠` - An open, extensible, wiki for your team. ([Source Code](https://github.com/outline/outline)) `BSD-3-Clause` `Nodejs`
 - [Pepperminty Wiki](https://github.com/sbrl/Pepperminty-Wiki) - Complete markdown-powered wiki contained in a single PHP file. ([Demo](https://starbeamrainbowlabs.com/labs/peppermint/build/)) `MPL-2.0` `PHP`