chore: checkpoint before Python removal

vendor/serde_json/tests/regression/issue1004.rs

@@ -0,0 +1,12 @@
+#![cfg(feature = "arbitrary_precision")]
+
+#[test]
+fn test() {
+    let float = 5.55f32;
+    let value = serde_json::to_value(float).unwrap();
+    let json = serde_json::to_string(&value).unwrap();
+
+    // If the f32 were cast to f64 by Value before serialization, then this
+    // would incorrectly serialize as 5.550000190734863.
+    assert_eq!(json, "5.55");
+}