Fix vertical_scroll_margin not being capped for large vertical_scroll_margin values (#15473)

When switching to function definitions in a new buffer the
`AutoscrollStrategy::Focused` being emitted to scroll to the found
location.
If a large value `vertical_scroll_margin` (e.g.: 99) is set, this leads
to an incorrectly calculated position and the new buffer opens in the
wrong place.

In `autoscroll_vertically()` there is a margin calculated to cap the
value of `vertical_scroll_margin` for certain AutoscrollStrategies. This
margin is being used in `AutoscrollStrategy::Fit` and
`AutoscrollStrategy::Newest` but was probably forgotten for
`AutoscrollStrategy::Focused`.

- Might fix [#15101](https://github.com/zed-industries/zed/issues/15101)

Release Notes:

- N/A

crates/editor/src/scroll/autoscroll.rs

@@ -189,8 +189,8 @@ impl Editor {
                 self.set_scroll_position_internal(scroll_position, local, true, cx);
             }
             AutoscrollStrategy::Focused => {
-                scroll_position.y =
-                    (target_top - self.scroll_manager.vertical_scroll_margin).max(0.0);
+                let margin = margin.min(self.scroll_manager.vertical_scroll_margin);
+                scroll_position.y = (target_top - margin).max(0.0);
                 self.set_scroll_position_internal(scroll_position, local, true, cx);
             }
             AutoscrollStrategy::Top => {