fix iosxr commands to encode json (#23346)

the command dict in the iosxr module_utils wasn't encoding the request
to json.  this patch will fix that problem

test/units/modules/network/iosxr/test_iosxr_command.py

@@ -45,8 +45,7 @@ class TestIosxrCommandModule(TestIosxrModule):
 
             for item in commands:
                 try:
-                    obj = json.loads(item)
-                    command = obj['command']
+                    command = item['command']
                 except ValueError:
                     command = item
                 filename = str(command).replace(' ', '_')