dependabot updating to non-existent nx versions

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Package ecosystem

npm

### Package manager version

_No response_

### Language version

_No response_

### Manifest location and content before the Dependabot update

package.json

### dependabot.yml content

_No response_

### Updated dependency

nx from 21.4.1 to 21.8.0

### What you expected to see, versus what you actually saw

dependabot is creating PRs to bump nx from 21.4.1 to 21.8.0 but since after the security incident all versions prior to 21.4.1 have been removed.
[https://github.com/nrwl/nx/security/advisories/GHSA-cxm3-wv7p-598c](https://github.com/nrwl/nx/security/advisories/GHSA-cxm3-wv7p-598c)

### Native package manager behavior

_No response_

### Images of the diff or a link to the PR, issue, or logs

_No response_

### Smallest manifest that reproduces the issue

_No response_

Start with the package.json manifest and reproduce the Dependabot update from nx 21.4.1 to 21.8.0, checking the package registry's available versions and the resulting pull request target. Done means Dependabot no longer proposes an unavailable nx version for this manifest.

Written by the indexing model from the issue text.