Deprecated dependencies and commands in 2022

[rcarrascoc]

Hi there!

In 2022, there're some dependencies and commands are deprecated for Python 3.9 or later, here are some updates:

In treenode_helper.py you should change:
line 5: from numba import autjit -> from numba import jit
line 73 self.leaf = numpy.zeros(n_crit, dtype=numpy.int) -> self.leaf = numpy.zeros(n_crit, dtype=int)
line 75 self.child = numpy.zeros(8, dtype=numpy.int) -> self.child = numpy.zeros(8, dtype=int)
line 79 self.multipole = numpy.zeros(10, dtype=numpy.float) -> self.multipole = numpy.zeros(10, dtype=float)

In 04_tree_construction.ipyn you should change in class cell():
self.leaf = numpy.zeros(n_crit, dtype=numpy.int) -> self.leaf = numpy.zeros(n_crit, dtype=int)
self.child = numpy.zeros(8, dtype=numpy.int) -> self.child = numpy.zeros(8, dtype=int)
self.multipole = numpy.zeros(10, dtype=numpy.float) -> self.multipole = numpy.zeros(10, dtype=float)

In 06_treecode.ipynb you should change every clock() to time()

I hope it will be helpful for future readers