Remove double-assignment of EC2 parameters (#4081)

The `source_dest_check` and `termination_protection` variables are being
assigned twice in ec2.py, likely due to an incorrect merge somewhere
along the line.

lib/ansible/modules/cloud/amazon/ec2.py

@@ -1267,8 +1267,6 @@ def startstop_instances(module, ec2, instance_ids, state, instance_tags):
     termination_protection = module.params.get('termination_protection')
     changed = False
     instance_dict_array = []
-    source_dest_check = module.params.get('source_dest_check')
-    termination_protection = module.params.get('termination_protection')
 
     if not isinstance(instance_ids, list) or len(instance_ids) < 1:
         # Fail unless the user defined instance tags