Downgrade nix, add it to Cargo.lock

This was necessary, to have minimum changes

Author: aminvakil

Cargo.lock

@@ -4168,6 +4168,7 @@ dependencies = [
  "hostname 0.4.1",
  "http",
  "mimalloc",
+ "nix",
  "relay-config",
  "relay-kafka",
  "relay-log",

relay/Cargo.toml

@@ -32,5 +32,5 @@ relay-statsd = { workspace = true }
 relay-kafka = { workspace = true, optional = true }
 uuid = { workspace = true }
 reqwest = { workspace = true, features = ["gzip", "native-tls-vendored"] }
-nix = { version = "0.31.2", features = ["signal"] }
+nix = { version = "0.29.0", features = ["signal"] }
 mimalloc = { workspace = true, features = ["v3", "override", "debug_in_debug"] }