Pinning SimpleITK version to 2.2.1.

Pinning SimpleITK version to the last version which was released with
binaries for Python 3.7.0 which is required by Imaris. Python version
3.7.0 reached end of life in June 27 2023, so newer versions of
SimpleITK do not have binaries for 3.7.0 and we don't want pip to try
and install from source.

Possibly install in stand-alone mode which doesn't depend on the
Python version required by Imaris. In this case we can use the
latest version of SimpleITK and just change the Python version to
something later than 3.7.0 (as of this writing 3.11 is recommended).

environment.yml

@@ -6,7 +6,7 @@ dependencies:
   - python=3.7.0 #Python version supported by imaris
   - pip
   - pip:
-    - SimpleITK >= 2.0.0
+    - SimpleITK == 2.2.1
     - numpy
     - pandas
     - h5py>=2.10.0