Update C++ SDK version to 11.0.0. (#1294)

Author: jonsimantov

cpp_sdk_version.json

@@ -1,5 +1,5 @@
 {
-  "released": "10.8.0",
-  "stable": "10.8.0",
-  "head": "10.8.0"
+  "released": "11.0.0",
+  "stable": "11.0.0",
+  "head": "11.0.0"
 }

release_build_files/readme.md

@@ -603,7 +603,7 @@ workflow use only during the development of your app, not for publicly shipping
 code.
 
 ## Release Notes
-### Upcoming Release
+### 11.0.0
 -   Changes
     - General: Update minimum supported C++ standard to C++14.
     - General (Android): Update to Firebase Android BoM version 31.5.0.