upgrade py3.10 syntax

Author: mcflugen

heat/bmi_heat.py

@@ -39,7 +39,7 @@ def initialize(self, filename=None):
         if filename is None:
             self._model = Heat()
         elif isinstance(filename, str):
-            with open(filename, "r") as file_obj:
+            with open(filename) as file_obj:
                 self._model = Heat.from_file_like(file_obj.read())
         else:
             self._model = Heat.from_file_like(filename)

heat/heat.py

@@ -53,7 +53,7 @@ def solve_2d(temp, spacing, out=None, alpha=1.0, time_step=1.0):
     return np.add(temp, out, out=out)
 
 
-class Heat(object):
+class Heat:
 
     """Solve the Heat equation on a grid.