Fix typo to allow Health Checks to use the Notes field.

Without this fix, Health Checks look like this (before):

    {                                                                                                 
    ...                                                    
        "Status": "passing",                                                                          
        "Notes": "",
        "Output": "[0, 11, 9]",                                                                                             
    ...
    },                                                                                                                      

and (after):

    {                                                                                                 
    ...                                                    
        "Status": "passing",                                                                          
        "Notes": "Percentages, warning levels: 'CPU' over 85%; 'Memory' over 85%; 'Root Disk' over 85%, every 20s, TTL 60s",
        "Output": "[0, 11, 9]",                                                                                             
     ...
    },