UI tests broken following Polkadot update.

[tomjeatt]

Our UI tests have stopped running following the changes to support the Polkadot 10.9.1 upgrade. This is specifically related to the polkadot update itself, not the lib or bridge (i.e. I tested by using the previous version of the UI changing only @polkadot/api
to 10.9.1—the tests failed).

The cause of the problem seems to be that jest can't find polkadot's x-textdecoder dependency:

 FAIL  src/test/pages/Loans/index.test.tsx
  ● Test suite failed to run

    ENOENT: no such file or directory, open 'node:util'

      at Runtime.readFile (node_modules/jest-runtime/build/index.js:1987:21)
      at Object.<anonymous> (node_modules/@polkadot/x-textdecoder/cjs/node.js:5:45)

This error is reported for every test suite.