All tests using jsdom fail with node >= 21

[Fil]

❯ nvm use 20
Now using node v20.3.0 (npm v9.6.7)
... tests OK...

❯ nvm use 21
Now using node v21.6.0 (npm v10.2.4)
❯ yarn && yarn test
...
  871) plot youngAdults:
     TypeError: Cannot set property navigator of #<Object> which has only a getter
      at Context.<anonymous> (file:///Users/fil/Sites/plot/test/jsdom.js:22:22)
      at process.processImmediate (node:internal/timers:478:21)