Revert "Set default shell on Windows to "powershell" (AcademySoftware…

…Foundation#1578)"

This reverts commit c700e99.

src/rez/rezconfig.py

@@ -565,9 +565,6 @@
 # The default shell type to use when creating resolved environments (eg when using
 # :ref:`rez-env`, or calling :meth:`.ResolvedContext.execute_shell`). If empty or None, the
 # current shell is used (for eg, "bash").
-#
-# .. versionchanged:: 3.0.0
-#    The default value on Windows was changed to "powershell".
 default_shell = ""
 
 # The command to use to launch a new Rez environment in a separate terminal (this

src/rez/system.py

@@ -65,16 +65,15 @@ def shell(self):
         """Get the current shell.
 
         Returns:
-            The current shell this process is running in (bash, tcsh, pwsh, etc). On Windows,
-            the return value is always "powershell".
+            The current shell this process is running in (bash, tcsh, pwsh, etc).
         """
         from rez.shells import get_shell_types
         shells = set(get_shell_types())
         if not shells:
             raise RezSystemError("no shells available")
 
         if self.platform == "windows":
-            return "powershell"
+            return "cmd"
         else:
             import subprocess as sp
             shell = None