Fix profile-sqlite feature build

Signed-off-by: Jacinta Ferrant <[email protected]>

stackslib/src/util_lib/db.rs

@@ -681,6 +681,7 @@ pub fn tx_begin_immediate_sqlite<'a>(conn: &'a mut Connection) -> Result<DBTx<'a
 
 #[cfg(feature = "profile-sqlite")]
 fn trace_profile(query: &str, duration: Duration) {
+    use serde_json::json;
     let obj = json!({"millis":duration.as_millis(), "query":query});
     debug!(
         "sqlite trace profile {}",