docs: Specific v3.10.0 version.

Change-Id: I9e7de1fa8c3815b29e3e1316bb99497d267cc1bc

Author: arriolac

README.md

@@ -32,7 +32,7 @@ for details on how to get an API Key.
 ## GoogleMapsBeta
 
 The `GoogleMapsBeta` and `GoogleMapsBeta-Swift` sub-directories contain sample code for the
-[Maps SDK for iOS BETA](https://developers.google.com/maps/documentation/ios-sdk/v310-beta) version of the library. 
+[Maps SDK for iOS v3.10.0 BETA](https://developers.google.com/maps/documentation/ios-sdk/v310-beta) version of the library.
 
 To use the Objective-C project: