build(deps): bump rand from 0.8.5 to 0.8.6 in /signer/tests/wasm

Bumps [rand](https://github.com/rust-random/rand) from 0.8.5 to 0.8.6.
- [Release notes](https://github.com/rust-random/rand/releases)
- [Changelog](https://github.com/rust-random/rand/blob/0.8.6/CHANGELOG.md)
- [Commits](rust-random/rand@0.8.5...0.8.6)

---
updated-dependencies:
- dependency-name: rand
  dependency-version: 0.8.6
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Cargo.toml

@@ -130,7 +130,7 @@ smoldot = { version = "1.1.0", default-features = false }
 smoldot-light = { version = "1.1.0", default-features = false }
 tokio-stream = "0.1.16"
 futures-util = "0.3.31"
-rand = "0.8.5"
+rand = "0.8.6"
 pin-project = "1.1.5"
 
 # Light client wasm: