build(rust): Update Rust toolchain to 1.90 (#2778)

Update Rust toolchain to 1.90 (1.90.0).

  **Changes:**
  - Update `rust-toolchain.toml` channel to `1.90`

**Release Notes:** https://github.com/rust-lang/rust/releases/tag/1.90.0

### Fixed lints

The following lints triggered after the update, they have been fixed:

```
warning: unnecessary parentheses around closure body
  --> src/commands/monitors/list.rs:20:30
   |
20 |     monitors.sort_by_key(|p| (p.name.clone()));
   |                              ^              ^
   |
   = note: `#[warn(unused_parens)]` on by default
help: remove these parentheses
   |
20 -     monitors.sort_by_key(|p| (p.name.clone()));
20 +     monitors.sort_by_key(|p| p.name.clone());
   |

warning: struct `GitHubAsset` is never constructed
    --> src/api/mod.rs:2181:8
     |
2181 | struct GitHubAsset {
     |        ^^^^^^^^^^^
     |
     = note: `#[warn(dead_code)]` on by default

warning: struct `GitHubRelease` is never constructed
    --> src/api/mod.rs:2187:8
     |
2187 | struct GitHubRelease {
     |        ^^^^^^^^^^^^^
```

  ---
🤖 *This PR was created automatically by the Rust toolchain update bot.*

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Daniel Szoke <daniel.szoke@sentry.io>

Author: github-actions[bot]

rust-toolchain.toml

@@ -1,4 +1,4 @@
 [toolchain]
 # We pin the minor version to prevent new Clippy lints from breaking CI.
 # But, we still want to pick up new patch versions.
-channel = "1.89"
+channel = "1.90"

src/api/mod.rs

@@ -2177,18 +2177,6 @@ pub struct ReleaseCommit {
     pub id: String,
 }
 
-#[derive(Debug, Serialize, Deserialize)]
-struct GitHubAsset {
-    browser_download_url: String,
-    name: String,
-}
-
-#[derive(Debug, Serialize, Deserialize)]
-struct GitHubRelease {
-    tag_name: String,
-    assets: Vec<GitHubAsset>,
-}
-
 #[derive(Debug, Serialize, Deserialize)]
 struct RegistryRelease {
     version: String,

src/commands/monitors/list.rs

@@ -17,7 +17,7 @@ pub fn execute(matches: &ArgMatches) -> Result<()> {
     let api = Api::current();
     let org = config.get_org(matches)?;
     let mut monitors = api.authenticated()?.list_organization_monitors(&org)?;
-    monitors.sort_by_key(|p| (p.name.clone()));
+    monitors.sort_by_key(|p| p.name.clone());
 
     let mut table = Table::new();
     table