Removing field keeping reference to HttpClientFactory
Removing field keeping reference to HttpClientFactory

Upon further thinking, I realized that we will not need to create the
HttpClient again during the life of FitbitClient, hence the reference is
not needed.

AlexGhiondea/Fitbit.NET,amammay/Fitbit.NET,amammay/Fitbit.NET,AlexGhiondea/Fitbit.NET,amammay/Fitbit.NET,AlexGhiondea/Fitbit.NET,aarondcoleman/Fitbit.NET,aarondcoleman/Fitbit.NET,WestDiscGolf/Fitbit.NET,WestDiscGolf/Fitbit.NET,aarondcoleman/Fitbit.NET,WestDiscGolf/Fitbit.NET