[css-scroll-snap] Fixup ascii art, since Tab's text editor doesn't have block selection mode. ;)

Author: fantasai

css-scroll-snap/Overview.bs

@@ -592,20 +592,20 @@ Snapping Boxes that Overflow the Scrollport</h4>
             │                     │  ┆
             │┌─── sub-section ───┐│  ╯ ━┓
             │└───────────────────┘│    2┃
-            │┌─── sub-section ───┐│     ┃ ━┓
-            ││                   ││    ━┛ 3┃
-            │└───────────────────┘│        ┃
-            │┌─── sub-section ───┐│ ━┓    ━┛
-            │└───────────────────┘│ 4┃
-            │┌─── sub-section ───┐│  ┃ ━┓
-            ││                   ││ ━┛ 5┃
-            ││                   ││     ┃
-            ││                   ││    ━┩
-            ││                   ││     ┆
-            ││                   ││     ┆
-            ││                   ││     ┆
-            │└───────────────────┘│     ┆
-            └─────────────────────┘     ╯
+            │┌─── sub-section ───┐│ ━┓  ┃
+            ││                   ││ 3┃ ━┛
+            │└───────────────────┘│  ┃
+            │┌─── sub-section ───┐│ ━┛ ━┓
+            │└───────────────────┘│    4┃
+            │┌─── sub-section ───┐│ ━┓  ┃
+            ││                   ││ 5┃ ━┛
+            ││                   ││  ┃
+            ││                   ││ ━┩
+            ││                   ││  ┆
+            ││                   ││  ┆
+            ││                   ││  ┆
+            │└───────────────────┘│  ┆
+            └─────────────────────┘  ╯
             </pre>
             <figcaption>
                 In the figure above,