Adjust names of negated style methods (#11453)

This PR adjusts the names of the negated style methods by moving the
`neg_` to after the property name instead of before.

This will help keep related style methods grouped together in
completions.

It also makes it a bit clearer that the negation applies to the value.

### Before

```rs
div()
    .neg_mx_1()
    .neg_mt_2()
```

### After

```rs
div()
    .mx_neg_1()
    .mt_neg_2()
```

Release Notes:

- N/A

crates/assistant2/src/assistant2.rs

@@ -620,7 +620,7 @@ impl AssistantChat {
             div()
                 .py_1()
                 .px_2()
-                .neg_mx_1()
+                .mx_neg_1()
                 .rounded_md()
                 .border_1()
                 .border_color(theme.status().error_border)