Fix import statement in tests with the latest node-fetch

[jakubkoci]

Dependabot wanted to update node-fetch #8. But there is the following error in the 3.3.1 version. I found it works fine with the version 2.6.11 we currently use. It would be good to figure out how to fix the issue so we're not stuck at that version. Or, we can just wait for the update of the library itself that would fix it.

    /home/runner/work/ssi-trust-registry/ssi-trust-registry/node_modules/node-fetch/src/index.js:9
    import http from 'node:http';
    ^^^^^^

    SyntaxError: Cannot use import statement outside a module

    > 1 | import fetch from 'node-fetch'
        | ^
      2 | import { startServer } from './server'
      3 | import { Server } from 'http'
      4 | import { AddressInfo } from 'net'

      at Runtime.createScriptFromCode (node_modules/jest-runtime/build/index.js:1495:14)
      at Object.<anonymous> (src/server.test.ts:1:1)

[rblaine95]

Potentially relevant documentation - https://github.com/node-fetch/node-fetch/blob/main/docs/v3-UPGRADE-GUIDE.md