Updated Spatial4n repository URL (#217)

Author: NightOwl888

README.md

@@ -87,7 +87,7 @@ Discuss Spatial4j on our [mailing list](https://locationtech.org/mailman/listinf
 
 View metadata about the project as generated by Maven: [maven site](https://locationtech.github.io/spatial4j/).
 
-Spatial4j has been ported to .NET (C#) where it is appropriately named [Spatial4n](https://github.com/synhershko/Spatial4n).
+Spatial4j has been ported to .NET (C#) where it is appropriately named [Spatial4n](https://github.com/Spatial4n/Spatial4n).
 
 ### Future Road Map Ideas