Bump SDK Extension version to 4

Modules with new APIs in this version are

  - AD_SERVICES
  - SDK_EXTENSIONS
  - TETHERING

Bug: 245513010
Test: manual install of modules
Change-Id: I8f4becf87001220a385df3b220e6929b2b212920
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index 3dc8965..8319b9b 100644
--- a/core/version_defaults.mk
+++ b/core/version_defaults.mk
@@ -78,7 +78,7 @@
 .KATI_READONLY := PLATFORM_SDK_VERSION
 
 # This is the sdk extension version of this tree.
-PLATFORM_SDK_EXTENSION_VERSION := 3
+PLATFORM_SDK_EXTENSION_VERSION := 4
 .KATI_READONLY := PLATFORM_SDK_EXTENSION_VERSION
 
 # This is the sdk extension version that PLATFORM_SDK_VERSION ships with.