minor: fixing typo

Author: Sam Kleinman

source/core/geospatial-indexes.txt

@@ -262,7 +262,7 @@ for geospatial information based on a sphere or earth.
      sphere (e.g. the Earth) in the same units as the distance
      measurement.
 
-   - *radians to distance*: multiply the rad ian measure by the radius
+   - *radians to distance*: multiply the radian measure by the radius
      of the sphere (e.g. the Earth) in the units system that you want to
      convert the distance to.