⬆️ micro: Update syn to v2.0.90 (#1164)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [syn](https://redirect.github.com/dtolnay/syn) | dependencies | patch
| `2.0.89` -> `2.0.90` |

---

### Release Notes

<details>
<summary>dtolnay/syn (syn)</summary>

###
[`v2.0.90`](https://redirect.github.com/dtolnay/syn/releases/tag/2.0.90)

[Compare
Source](https://redirect.github.com/dtolnay/syn/compare/2.0.89...2.0.90)

- Fix automatic parenthesization of subexpressions containing outer
attributes, such as `(#[attr] thing).field`
([#&#8203;1785](https://redirect.github.com/dtolnay/syn/issues/1785))
- Fix automatic parenthesization of function calls via a struct field,
such as `(thing.field)()` and `thing.0()`
([#&#8203;1786](https://redirect.github.com/dtolnay/syn/issues/1786))

</details>

---

### Configuration

📅 **Schedule**: Branch creation - At any time (no schedule defined),
Automerge - At any time (no schedule defined).

🚦 **Automerge**: Enabled.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the
rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update
again.

---

- [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check
this box

---

This PR was generated by [Mend Renovate](https://mend.io/renovate/).
View the [repository job
log](https://developer.mend.io/github/dbus2/zbus).

<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzOS4xOS4wIiwidXBkYXRlZEluVmVyIjoiMzkuMTkuMCIsInRhcmdldEJyYW5jaCI6Im1haW4iLCJsYWJlbHMiOltdfQ==-->

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>