Update version numbers for 11.6.0 release. (#1466)

Author: jonsimantov

cpp_sdk_version.json

@@ -1,5 +1,5 @@
 {
-  "released": "11.5.0",
-  "stable": "11.5.0",
-  "head": "11.5.0"
+  "released": "11.6.0",
+  "stable": "11.6.0",
+  "head": "11.6.0"
 }

release_build_files/readme.md

@@ -10,7 +10,7 @@ on *iOS* and *Android*:
 *   Firebase Dynamic Links
 *   Cloud Firestore
 *   Firebase Functions
-*   Google Mobile Ads
+*   Google Mobile Ads (with User Messaging Platform)
 *   Firebase Installations
 *   Firebase Instance ID (deprecated SDK)
 *   Firebase Realtime Database
@@ -631,8 +631,9 @@ workflow use only during the development of your app, not for publicly shipping
 code.
 
 ## Release Notes
-### Next Release
+### 11.6.0
 -   Changes
+    - General (iOS): Update to Firebase Cocoapods version 10.16.0.
     - Firestore: Add support for disjunctions in queries (OR queries)
       ([#1453](https://github.com/firebase/firebase-cpp-sdk/pull/1453)).
     - GMA: Added the User Messaging Platform (UMP) SDK, required for obtaining