Remove redundant VTable::child overrides

Both Patched and PythonVTable overrode VTable::child with behavior
identical to the trait default: all four Patched slots are required
(always Some), so the default idx-th non-None slot lookup returns
exactly slots[idx], and PythonArray has no slots with nchildren() == 0,
so its panicking override was unreachable behind the idx < nchildren
guard in every caller.

Signed-off-by: "Joe Isaacs" <joe.isaacs@live.co.uk>
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XbjnDVZQ9KqXgAAhxy9g7D

Author: joseph-isaacs

vortex-array/src/arrays/patched/vtable/mod.rs

@@ -138,16 +138,6 @@ impl VTable for Patched {
         with_empty_buffers(self, array, buffers)
     }
 
-    fn child(array: ArrayView<'_, Self>, idx: usize) -> ArrayRef {
-        match idx {
-            PatchedSlots::INNER => array.inner().clone(),
-            PatchedSlots::LANE_OFFSETS => array.lane_offsets().clone(),
-            PatchedSlots::PATCH_INDICES => array.patch_indices().clone(),
-            PatchedSlots::PATCH_VALUES => array.patch_values().clone(),
-            _ => vortex_panic!("invalid child index for PatchedArray: {idx}"),
-        }
-    }
-
     fn serialize(
         array: ArrayView<'_, Self>,
         _session: &VortexSession,

vortex-python/src/arrays/py/vtable.rs

@@ -96,10 +96,6 @@ impl VTable for PythonVTable {
         0
     }
 
-    fn child(_array: ArrayView<'_, Self>, idx: usize) -> ArrayRef {
-        vortex_panic!("PythonArray child index {idx} out of bounds")
-    }
-
     fn child_name(_array: ArrayView<'_, Self>, idx: usize) -> String {
         vortex_panic!("PythonArray child_name index {idx} out of bounds")
     }