Fix build failure with minimal-versions

```
  error[E0599]: no function or associated item named `from_pid` found for struct `Process` in the current scope
     --> src/reactor/kqueue.rs:66:35
      |
  66  |                 unsafe { Process::from_pid(*pid, ProcessOps::Exit) },
      |                                   ^^^^^^^^ function or associated item not found in `Process<'_>`
      |
```

Author: taiki-e

Cargo.toml

@@ -32,7 +32,7 @@ concurrent-queue = "2.2.0"
 futures-io = { version = "0.3.28", default-features = false, features = ["std"] }
 futures-lite = { version = "2.0.0", default-features = false }
 parking = "2.0.0"
-polling = "3.0.0"
+polling = "3.4.0"
 rustix = { version = "1.0.7", default-features = false, features = ["fs", "net", "std"] }
 slab = "0.4.2"
 tracing = { version = "0.1.37", default-features = false, optional = true }