Update examples in docstrings to support Numpy 2

Convert Numpy scalars to Python numbers so the outputs of examples that
are being compared when running doctests support Numpy>=2.0.

harmonica/_equivalent_sources/gradient_boosted.py

@@ -142,7 +142,7 @@ def estimate_required_memory(self, coordinates):
 
         Returns
         -------
-        memory_required : float
+        memory_required : int
             Amount of memory required to store the largest Jacobian matrix in
             bytes.
 
@@ -157,7 +157,8 @@ def estimate_required_memory(self, coordinates):
         ...     random_state=42,
         ... )
         >>> eqs = EquivalentSourcesGB(window_size=2e3)
-        >>> eqs.estimate_required_memory(coordinates)
+        >>> n_bytes = eqs.estimate_required_memory(coordinates)
+        >>> int(n_bytes)
         9800
         """
         # Build the sources and assign the points_ attribute

harmonica/_forward/prism_layer.py

@@ -107,11 +107,13 @@ def prism_layer(
         coords_units:      meters
         properties_units:  SI
     >>> # Get the boundaries of the layer (will exceed the region)
-    >>> print(prisms.prism_layer.boundaries)
-    (-1.25, 11.25, 1.0, 9.0)
+    >>> boundaries = prisms.prism_layer.boundaries
+    >>> list(float(b) for b in boundaries)
+    [-1.25, 11.25, 1.0, 9.0]
     >>> # Get the boundaries of one of the prisms
-    >>> print(prisms.prism_layer.get_prism((0, 2)))
-    (3.75, 6.25, 1.0, 3.0, 0.0, 2.0)
+    >>> prism = prisms.prism_layer.get_prism((0, 2))
+    >>> list(float(b) for b in prism)
+    [3.75, 6.25, 1.0, 3.0, 0.0, 2.0]
     """  # noqa: W505
     dims = ("northing", "easting")
     # Initialize data and data_names as None