Update whisk requirement from 0.12 to 0.13

Updates the requirements on [whisk](https://github.com/ardaku/whisk) to permit the latest version.
- [Changelog](https://github.com/ardaku/whisk/blob/stable/CHANGELOG.md)
- [Commits](ardaku/whisk@v0.12.0...v0.13.0)

---
updated-dependencies:
- dependency-name: whisk
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Cargo.toml

@@ -20,7 +20,7 @@ optional = true
 [dev-dependencies]
 async_main = { version = "0.4", features = ["pasts"] }
 async-std = "1.11"
-whisk = "0.12"
+whisk = "0.13"
 
 [target.'cfg(all(target_arch="wasm32", target_os="unknown"))'.dev-dependencies]
 wasm-bindgen = "0.2"