Remove unnecessary trailing slash

Author: RaoOfPhysics

config.yaml

@@ -26,7 +26,7 @@ life_cycle: pre-alpha
 license: CC-BY 4.0
 
 # Link to the source repository for this lesson
-source: https://github.com/r-devel/r-bug-tracking-lesson/
+source: https://github.com/r-devel/r-bug-tracking-lesson
 
 # URL of the live lesson
 url: https://contributor.r-project.org/r-bug-tracking-lesson/