changed link for data visualization

Author: mistrm82

index.md

@@ -48,7 +48,7 @@ in working with {{page.domain %}} data in {{page.topic %}}.
 3. [Lesson 02 Starting with data](02-starting-with-data.html)
 4. [Lesson 03 Introducing `data.frame`](03-data-frames.html)
 5. [Lesson 04 Aggregating and analyzing data with dplyr](04-dplyr.html)
-6. [Lesson 05 Data visualisation with ggplot2](05-visualisation-ggplot2.html)
+6. [Lesson 05 Data visualisation with ggplot2](05-data-visualization.html)
 
 ## Data