update release version to 9.4.0 (#1050)

Updates the release version to `9.4.0` in `release_build_files/readme.md` and in `cpp_sdk_version.json`.

Author: DellaBitta

cpp_sdk_version.json

@@ -1,5 +1,5 @@
 {
-  "released": "9.3.0",
-  "stable": "9.3.0",
-  "head": "9.3.0"
+  "released": "9.4.0",
+  "stable": "9.4.0",
+  "head": "9.4.0"
 }

release_build_files/readme.md

@@ -634,7 +634,7 @@ workflow use only during the development of your app, not for publicly shipping
 code.
 
 ## Release Notes
-### Upcoming Release
+### 9.4.0
 -   Changes
     - General (Desktop): Fixed an issue with embedded dependencies that could
       cause duplicate symbol linker errors in conjunction with other libraries