update readme tutorial 6

tutorials/README.md

@@ -7,7 +7,7 @@ In this folder we collect useful tutorials in order to understand the principles
 | Description   | Tutorial |
 |---------------|-----------|
 Introduction to PINA for Physics Informed Neural Networks training|[[.ipynb](tutorial1/tutorial.ipynb), [.py](tutorial1/tutorial.py), [.html](http://mathlab.github.io/PINA/_rst/tutorial1/tutorial.html)]|
-Building custom geometries with PINA `Location` class|[[.ipynb](tutorial1/tutorial.ipynb), [.py](tutorial1/tutorial.py), [.html](https://mathlab.github.io/PINA/_rst/tutorials/tutorial1/tutorial.html)]|
+Building custom geometries with PINA `Location` class|[[.ipynb](tutorial6/tutorial.ipynb), [.py](tutorial6/tutorial.py), [.html](https://mathlab.github.io/PINA/_rst/tutorials/tutorial6/tutorial.html)]|
 
 
 ## Physics Informed Neural Networks