cargo: Bump rustc to 1.89 (#36818)

Update Rustc to 1.89.

Reviewable by commit.

Leftover work:
- #37330 
- #38777

---------

Signed-off-by: sagudev <16504129+sagudev@users.noreply.github.com>
Co-authored-by: sagudev <16504129+sagudev@users.noreply.github.com>

components/script/dom/bindings/refcounted.rs

@@ -114,8 +114,7 @@ impl TrustedPromise {
                 self.owner_thread,
                 live_references as *const _ as *const libc::c_void
             );
-            // Borrow-check error requires the redundant `let promise = ...; promise` here.
-            let promise = match live_references
+            match live_references
                 .promise_table
                 .borrow_mut()
                 .entry(self.dom_object)
@@ -133,8 +132,7 @@ impl TrustedPromise {
                     promise
                 },
                 Vacant(_) => unreachable!(),
-            };
-            promise
+            }
         })
     }