mdformat incorrectly removes link references that are only used in admonitions

[devmcp]

Describe the bug

context
When I run mdformat on the following:

```{note}
Hello mdformat[^myref]
```

[^myref]: my ref here

expectation
I expected nothing to occur.

bug
But instead the reference gets removed leaving:

```{note}
Hello mdformat[^myref]
```

Reproduce the bug

See above

List your environment

No response

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[hukkin]

Thanks for the issue!

This is an issue with MyST syntax and mdformat-myst only, so I've moved the issue.