fix: Don't deep clone manuallydrop in GroupsPosition

crates/polars-core/src/frame/group_by/position.rs

@@ -582,7 +582,7 @@ impl<'a> ParallelIterator for GroupsTypeParIter<'a> {
     }
 }
 
-#[derive(Clone, Debug)]
+#[derive(Debug)]
 pub struct GroupPositions {
     sliced: ManuallyDrop<GroupsType>,
     // Unsliced buffer
@@ -591,6 +591,19 @@ pub struct GroupPositions {
     len: usize,
 }
 
+impl Clone for GroupPositions {
+    fn clone(&self) -> Self {
+        let sliced = slice_groups_inner(&self.original, self.offset, self.len);
+
+        Self {
+            sliced,
+            original: self.original.clone(),
+            offset: self.offset,
+            len: self.len,
+        }
+    }
+}
+
 impl PartialEq for GroupPositions {
     fn eq(&self, other: &Self) -> bool {
         self.offset == other.offset && self.len == other.len && self.sliced == other.sliced