Infrastructure: Failing link-checker for GitHub links

[ccanash]

First noted at #2775 (comment) (although it does affect any new contributions as well, at this time)

The failing build's error message is Found broken external link on content/about/contributing/contributing.html:69:15, hash not found on page, which points to https://github.com/w3c/aria-practices#code-conformance.

[howard-e]

An additional failing check here first happening yesterday, is the following:

error stack for chrome.google link

Found broken external link on content/patterns/landmarks/examples/at.html:198:21
  FetchError: maximum redirect reached at: https://chrome.google.com/webstore/detail/skipto-landmarks-headings/fjkpbfcodhflpdildjbmdhhmcoplghgf
    at ClientRequest.<anonymous> (/home/runner/work/aria-practices/aria-practices/node_modules/node-fetch/lib/index.js:1590:15)
    at ClientRequest.emit (node:events:529:35)
    at HTTPParser.parserOnIncomingClient (node:_http_client:700:27)
    at HTTPParser.parserOnHeadersComplete (node:_http_common:119:17)
    at TLSSocket.socketOnData (node:_http_client:541:22)
    at TLSSocket.emit (node:events:517:28)
    at addChunk (node:internal/streams/readable:368:12)
    at readableAddChunk (node:internal/streams/readable:341:9)
    at Readable.push (node:internal/streams/readable:278:10)
    at TLSWrap.onStreamRead (node:internal/stream_base_commons:190:23)
Link checker found 1 broken link

The link hasn't been updated; it seems some new rate limit is being hit?