STYLE: Prefer specifying b-values as integer types

Prefer specifying b-values as integer types. Increases consistency with
the rest of the code, and avoids using `numbers.Number` which seems to
be problematic for type checking with `mypy`:
python/mypy#3186

Co-authored-by: Chris Markiewicz <[email protected]>

Author: jhlegarreta

src/nifreeze/model/dmri.py

@@ -21,7 +21,6 @@
 #     https://www.nipreps.org/community/licensing/
 #
 
-import numbers
 from importlib import import_module
 
 import numpy as np
@@ -179,8 +178,8 @@ def __init__(
         self,
         dataset: DWI,
         stat: str = "median",
-        th_low: numbers.Number = 100,
-        th_high: numbers.Number = 100,
+        th_low: int = 100,
+        th_high: int = 100,
         detrend: bool = False,
         **kwargs,
     ):
@@ -189,10 +188,10 @@ def __init__(
 
         Parameters
         ----------
-        th_low : :obj:`numbers.Number`
+        th_low : :obj:`int`
             A lower bound for the b-value corresponding to the diffusion weighted images
             that will be averaged.
-        th_high : :obj:`numbers.Number`
+        th_high : :obj:`int`
             An upper bound for the b-value corresponding to the diffusion weighted images
             that will be averaged.
         detrend : :obj:`bool`