Add what's new in 2.0.0 to the About popup

The layout test lets the changelog grow in height with its text, and still
checks its position and width.

tests/integration/test_layout_unchanged.gd

@@ -68,6 +68,12 @@ const RENAMED_PATHS: Dictionary = {
 			SYNC_COLUMNS + "/CaughtErrorsVBox/CaughtErrorsLabel",
 }
 
+## Nodes whose height follows text that changes between versions, such as the changelog.
+## Their position and width are still checked.
+const HEIGHT_FOLLOWS_TEXT: Array[String] = [
+	"AboutPopup/AboutPanel/ScrollContainer/ContentVBox",
+]
+
 ## How far a node may be from its old place, in pixels.
 const TOLERANCE: float = 0.5
 
@@ -134,7 +140,8 @@ func test_every_node_is_where_it_was() -> void:
 				problems.append("%s: %s is missing (was %s)" % [state, path, old_path])
 				continue
 			var rect: Array = actual[path].rect
-			for i: int in 4:
+			var sides: int = 3 if _height_follows_text(path) else 4
+			for i: int in sides:
 				if absf(rect[i] - expected.rect[i]) > TOLERANCE:
 					problems.append("%s: %s is at %s, was %s"
 							% [state, path, rect, expected.rect])
@@ -145,3 +152,8 @@ func test_every_node_is_where_it_was() -> void:
 	assert_array(problems).override_failure_message(
 			"%d nodes moved:\n%s" % [problems.size(), "\n".join(problems.slice(0, 30))]) \
 			.is_empty()
+
+
+static func _height_follows_text(path: String) -> bool:
+	return HEIGHT_FOLLOWS_TEXT.any(func(node_path: String) -> bool:
+		return path == node_path || path.begins_with(node_path + "/"))