export tutorials changed in c161138 (#498)

Co-authored-by: dario-coscia <dario-coscia@users.noreply.github.com>

tutorials/tutorial13/tutorial.ipynb

@@ -38,7 +38,7 @@
     "import warnings\n",
     "\n",
     "from pina import Condition, Trainer\n",
-    "from pina.problem import SpatialProblem \n",
+    "from pina.problem import SpatialProblem\n",
     "from pina.operator import laplacian\n",
     "from pina.solver import PINN, SelfAdaptivePINN as SAPINN\n",
     "from pina.loss import LpLoss\n",

tutorials/tutorial13/tutorial.py

@@ -13,7 +13,7 @@
 #
 # First of all, some useful imports.
 
-# In[1]:
+# In[ ]:
 
 
 ## routine needed to run the notebook on Google Colab