Tests: Switch to an updated fork of promises-aplus-tests

The upstream package has been unmaintained for years, with dependencies
with long-reported security issues. Switching to a fork allows to resolve
all the security reports against the jQuery development environment.

The fork is maintained by @mgol and has the following changes:
1. The `underscore` dependency has been removed.
2. `sinon` has been updated from v1 to v19.
3. `mocha` has been updated from v2 to v10.

Changes to the source are minimal; it will be easy to rebase the fixes
if the upstream package is ever updated.

In addition to the above, the `q` dependency has been removed.
It's been added in jquerygh-1996 but never really used.

Closes jquerygh-5559

Author: mgol