Update Rust crate tokio to v1.21.0 (#5184)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

Cargo.lock

@@ -78,7 +78,7 @@ swirl = { git = "https://github.com/sgrif/swirl.git", rev = "e87cf37" }
 tar = "=0.4.38"
 tempfile = "=3.3.0"
 thiserror = "=1.0.33"
-tokio = { version = "=1.20.1", features = ["net", "signal", "io-std", "io-util", "rt-multi-thread", "macros"]}
+tokio = { version = "=1.21.0", features = ["net", "signal", "io-std", "io-util", "rt-multi-thread", "macros"]}
 toml = "=0.5.9"
 tracing = "=0.1.36"
 tracing-subscriber = { version = "=0.3.15", features = ["env-filter"] }
@@ -91,7 +91,7 @@ conduit-test = "=0.10.0"
 hyper-tls = "=0.5.0"
 insta = { version = "=1.19.1", features = ["redactions", "yaml"] }
 once_cell = "=1.14.0"
-tokio = "=1.20.1"
+tokio = "=1.21.0"
 tower-service = "=0.3.2"
 
 [build-dependencies]