Update Rust crate serde to 1.0.209

Author: renovate[bot]

git-fast-import/Cargo.toml

@@ -10,5 +10,5 @@ license = "Apache-2.0"
 derive_more = "0.99.17"
 nom = "7.1.0"
 rev_lines = "0.2.1"
-serde = "1.0.136"
+serde = "1.0.209"
 thiserror = "1.0.30"

internal/state/Cargo.toml

@@ -9,7 +9,7 @@ bincode = "1.3.3"
 derive_more = "0.99.17"
 git-fast-import = { path = "../../git-fast-import" }
 log = "0.4.14"
-serde = { version = "1.0.136", features = ["derive", "rc"] }
+serde = { version = "1.0.209", features = ["derive", "rc"] }
 speedy = "0.8.1"
 thiserror = "1.0.30"
 tokio = { version = "1.16.1", features = ["io-util", "sync"] }