Update cars-assemble.jl (#888)

Change indentation to four spaces

Author: depial

exercises/concept/cars-assemble/cars-assemble.jl

@@ -1,11 +1,11 @@
 function success_rate(speed)
-  
+    
 end
 
 function production_rate_per_hour(speed)
-  
+    
 end
 
 function working_items_per_minute(speed)
-  
+    
 end