build(deps): bump tokio from 1.20.3 to 1.20.4 in /ch_03/tricoder

Bumps [tokio](https://github.com/tokio-rs/tokio) from 1.20.3 to 1.20.4.
- [Release notes](https://github.com/tokio-rs/tokio/releases)
- [Commits](https://github.com/tokio-rs/tokio/compare/tokio-1.20.3...tokio-1.20.4)

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

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

ch_03/tricoder/Cargo.lock

@@ -822,9 +822,9 @@ checksum = "cda74da7e1a664f795bb1f8a87ec406fb89a02522cf6e50620d016add6dbbf5c"
 
 [[package]]
 name = "tokio"
-version = "1.20.3"
+version = "1.20.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "664cf6576f16c0ad68184998f3c2d4be9903ede6b291a5b5cfc97d29e0057283"
+checksum = "eb78f30e4b41e98ca4cce5acb51168a033839a7af9e42b380355808e14e98ee0"
 dependencies = [
  "autocfg",
  "bytes",