### Godot version

4.1.1

### System information

linux

### Issue description

The `"%+f"` format adds a `+` sign in front of positive numbers. If you try to format `-0.0`, it breaks and displays both a `+` and a `-`.

### Steps to reproduce

```gdscript
@tool
extends EditorScript

func _run() -> void:
    print("%+f" % -0.0)
```

### Minimal reproduction project

see above
String s = "Mars,Jupiter,Saturn,Uranus";
	const char *slices[4] = { "Mars", "Jupiter", "Saturn", "Uranus" };
	for (int i = 0; i < s.get_slice_count(","); i++) {
		CHECK(s.get_slice(",", i) == slices[i]);
	}
}
TEST_CASE("[String] Splitting") {
	String s = "Mars,Jupiter,Saturn,Uranus";
	Vector<String> l;
	const char *slices_l[3] = { "Mars", "Jupiter", "Saturn,Uranus" };
	const char *slices_r[3] = { "Mars,Jupiter", "Saturn", "Uranus" };
	const char *slices_3[4] = { "t", "e", "s", "t" };
	l = s.split(",", true, 2);
	CHECK(l.size() == 3);
	for (int i = 0; i < l.size(); i++) {
		CHECK(l[i] == slices_l[i]);
	}
	l = s.rsplit(",", true, 2);
	CHECK(l.size() == 3);
	for (int i = 0; i < l.size(); i++) {
		CHECK(l[i] == slices_r[i]);
	}
	s = "test";
	l = s.split();
	CHECK(l.size() == 4);
	for (int i = 0; i < l.size(); i++) {
		CHECK(l[i] == slices_3[i]);
	}
	s = "";
	l = s.split();