Update docs

Co-authored-by: Dongdong Tian <seisman.info@gmail.com>

Author: yvonnefroehlich

pygmt/datasets/earth_free_air_anomaly.py

@@ -79,7 +79,7 @@ def load_earth_free_air_anomaly(
     Returns
     -------
     grid
-        The Earth free-air anomaly grid. Coordinates are latitude and longitude in
+        The Earth free-air anomaly grid (or its uncertainty). Coordinates are latitude and longitude in
         degrees. Units are in mGal.
 
     Note