Don’t extend the column size to the bottom of the page

It’s normal for the first columns to be broken, there’s no need to extend their
sizes to reach the bottom of the page as we do for "normal" blocks.

weasyprint/layout/block.py

@@ -750,7 +750,7 @@ def block_container_layout(context, box, bottom_space, skip_stack,
         # new_box.height
         new_box.height = max(
             min(new_box.height, new_box.max_height), new_box.min_height)
-    elif bottom_space > -inf:
+    elif bottom_space > -inf and not new_box.is_column:
         # Make the box fill the blank space at the bottom of the page
         # https://www.w3.org/TR/css-break-3/#box-splitting
         new_box.height = (