gpui: Rename rounded_md to rounded_sm (#26228)

This PR renames the `rounded_md` style method to `rounded_sm`.

Follow up to https://github.com/zed-industries/zed/pull/26221, which
freed up the `rounded_sm` name.

Release Notes:

- N/A

crates/ui/src/components/indicator.rs

@@ -77,7 +77,7 @@ impl RenderOnce for Indicator {
             IndicatorKind::Bar => container
                 .w_full()
                 .h_1p5()
-                .rounded_t_md()
+                .rounded_t_sm()
                 .bg(self.color.color(cx)),
         }
     }