Make tempfile a dev-dependency

Author: mbuesch

disktest-lib/Cargo.toml

@@ -23,6 +23,8 @@ rand = { workspace = true }
 rand_chacha = { workspace = true }
 ring = { workspace = true }
 signal-hook = { workspace = true }
+
+[dev-dependencies]
 tempfile = { workspace = true }
 
 [lints.clippy]