NDVI Anomaly notebook update

[lisarebelo]

https://github.com/digitalearthafrica/deafrica-sandbox-notebooks/blob/main/Datasets/NDVI_Anomaly.ipynb
Edits needed due to change in service name.

Change:

Digital Earth Africa's Monthly NDVI Anomaly service provides an estimate of vegetation condition, for each calendar month, against the long-term baseline condition measured for the month from 1984 to 2020

To:

Digital Earth Africa's Monthly NDVI and Anomalies service provides an estimate of vegetation condition for each calendar month, as well as comparison of this against the long-term baseline condition measured for the month over the period 1984 to 2020

Change all text:

NDVI Anomaly product

To:

NDVI and Anomalies product