chore: remove test_package_updates.yml workflow

The job is failing somewhat randomly on PRs where the code change is not
actually causing the failure.

The `test_package_updates.yml` workflow is not providing much value:

- The result is mostly determined by external factors like new package versions
  appearing on `npmjs.com`, not by the code changes in the PR. This is a
  frustrating experience for developers.
- The workflow seeks to simulate downstream installs by removing the
  `yarn.lock` file. However, this is not a realistic simulation. We have
  a toplevel `package.json` file with quite a long a `resolutions` section
  that overrides many package versions. Without it, the workflow would
  fail. Downstream projects do not take these resolutions into account,
  so the `yarn.lock` removal is a bit pointless.
  If there are downstream problems due to incorrect package versions, they have
  to submit a bug report instead.

Let's get rid of this workflow.

Issue: BTC-2170

Author: OttoAllmendinger