Allow Admin users to update an existing import source file in a model in deployed mode

Description:

1. Currently it is possible to change an import source file in a deployed model by running the import from a button published to a dashboard (clicking to run will prompt for a file to be uploaded).

2. Trying to change the import source file as an admin user, by going to Manage Import Data Sources and uploading a new file with the same name, and same file options will return the dialog "Deployed Mode is enabled for this model. You do not have permission to change structural data". The file does still get uploaded to the model (replacing the existing file).

These two actions are effectively performing the same task however the second returns a dialog stating you cannot change structural data in a deployed model.

The enhancement would be to allow the admin user to upload a new file to Manage Import Data Sources, with the same name and file options and which replaces the existing file for that import, but not return the dialog stating "Deployed Mode is enabled for this model. You do not have permission to change structural data."

To reproduce:
Put a model in deployed mode, then go to Actions, Manage Import Data Sources, and click Upload New File...
Upload a file with exactly the same name/format as one which already exists, and which will match the import definition.
Click Next, dialog box shows "Deployed Mode is enabled for this model. You do not have permission to change structural data."
Now try running the import to which that file relates - the import will run with the data from the file you have just uploaded, despite what the previous dialog message has displayed.