Update the dead links.

docs/source/userguide/beginners_guide.rst

@@ -30,7 +30,7 @@ Your first FESTIM script
 ------------------------
 
 
-Follow `this tutorial <https://github.com/festim-dev/FESTIM-workshop/blob/main/tasks/task1.ipynb>`_ to learn how
+Follow `this tutorial <https://github.com/festim-dev/FESTIM-workshop/blob/main/tasks/task01.ipynb>`_ to learn how
 to run a simple 1D diffusion problem in steady state with an homogeneous temperature, a volumetric source of hydrogen,
 and the concentration fixed at zero at boundaries.
 

docs/source/userguide/materials.rst

@@ -49,4 +49,4 @@ Integration with HTM
 
 H-transport-materials (HTM) is a Python database of hydrogen transport properties.
 Using this database will avoid making copy-pasting errors and add consistency across simulations by making sure the same properties are used.
-HTM can be easily `integrated with FESTIM <https://github.com/festim-dev/FESTIM-workshop/blob/main/tasks/task8.ipynb>`_.
+HTM can be easily `integrated with FESTIM <https://github.com/festim-dev/FESTIM-workshop/blob/main/tasks/task08.ipynb>`_.

docs/source/userguide/sources.rst

@@ -43,7 +43,7 @@ Hydrogen implanted in a material can be simulated by a Gaussian-shaped volumetri
             ),
         ]
 
-This class is used in `this tutorial <https://github.com/festim-dev/FESTIM-workshop/blob/main/tasks/task2.ipynb>`_.
+This class is used in `this tutorial <https://github.com/festim-dev/FESTIM-workshop/blob/main/tasks/task02.ipynb>`_.
 
 
 Radioactive decay