Fixed link

src/docs/part3/simulating_detectors.md

@@ -19,7 +19,7 @@ benefits.
 1. `ddsim` - a robust python program that is highly configurable. Good for 
    running quick simulations using built-in detector constructions, built-in 
    hit data model, and built-in sensitive detectors (tracker or calorimeter).  
-   We used `ddsim` in [part 1](part1/simple_detector) of this tutorial. See 
+   We used `ddsim` in [part 1](../part1/simple_detector) of this tutorial. See 
    `ddsim -h` for more details.
 2. Manual configuring the DDG4 setup. This can be achieved using XML, C++ (eg 
    in a ROOT script), or using the python interface. As we will see, this