There seems to have been no actual development activity on the spreadsheet extension in 5 years (May 2013), mostly just the upstream changes to it's git submodules, as they're unpinned
Time for it to go away?
- Archive Extension documentation page on mediawiki.org. https://www.mediawiki.org/wiki/Extension:Spreadsheet
- Remove submodule from mediawiki/extensions.git.
- Remove Jenkins pipeline from zuul/layout.yaml file in integration/config.git.
- Remove extension from groups/MediaWiki/mediawiki-extensions.txt file in translatewiki.net.
- Empty repository, add ARCHIVED.md.
- Mark the repository read-only in Gerrit, and prefix description with [ARCHIVED].
- Archive the repo mirror in Phabricator Diffusion: rESSH extension-Spreadsheet.
- Delete the repo mirror on GitHub.com: https://github.com/wikimedia/mediawiki-extensions-Spreadsheet