sway_text_node: Apply max_width when rendering

max_width was applied to the source box, but not to the cairo surface.
The cairo surface would therefore take on arbitrarily large dimensions
according to the required dimensions to fit the text input, which if
large enough would cause failures during output rendering and leave a
black hole in the titlebar.

sway/sway_text_node.c

@@ -87,7 +87,7 @@ static void render_backing_buffer(struct text_buffer *buffer) {
 	}
 
 	float scale = buffer->scale;
-	int width = ceil(buffer->props.width * scale);
+	int width = ceil(get_text_width(&buffer->props) * scale);
 	int height = ceil(buffer->props.height * scale);
 	float *color = (float *)&buffer->props.color;
 	float *background = (float *)&buffer->props.background;