Update dependency typedoc-plugin-markdown to v4.6.4 (#1300)

This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [typedoc-plugin-markdown](https://typedoc-plugin-markdown.org)
([source](https://redirect.github.com/typedoc2md/typedoc-plugin-markdown/tree/HEAD/packages/typedoc-plugin-markdown))
| [`4.6.3` ->
`4.6.4`](https://renovatebot.com/diffs/npm/typedoc-plugin-markdown/4.6.3/4.6.4)
|
[![age](https://developer.mend.io/api/mc/badges/age/npm/typedoc-plugin-markdown/4.6.4?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![adoption](https://developer.mend.io/api/mc/badges/adoption/npm/typedoc-plugin-markdown/4.6.4?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![passing](https://developer.mend.io/api/mc/badges/compatibility/npm/typedoc-plugin-markdown/4.6.3/4.6.4?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![confidence](https://developer.mend.io/api/mc/badges/confidence/npm/typedoc-plugin-markdown/4.6.3/4.6.4?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|

---

### Release Notes

<details>
<summary>typedoc2md/typedoc-plugin-markdown
(typedoc-plugin-markdown)</summary>

###
[`v4.6.4`](https://redirect.github.com/typedoc2md/typedoc-plugin-markdown/blob/HEAD/packages/typedoc-plugin-markdown/CHANGELOG.md#464)

[Compare
Source](https://redirect.github.com/typedoc2md/typedoc-plugin-markdown/compare/[email protected]@4.6.4)

##### Patch Changes

-   Added theme translations for "de" locale.
- Fix navigation items without group or categories
(`@group/@&#8203;category=none`)
([#&#8203;815](https://redirect.github.com/typedoc2md/typedoc-plugin-markdown/issues/815)).
-   Correctly handle sidebar groups for packages with merged modules.

</details>

---

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