Version bump for SdkExtensions

MTS is failing to install SdkExtensions as the version is lower than
the preinstalled version has a higher version code than the dev one.

Bug: 193059742
Bug: 194157158
Test: build & aapt dump badging <apex>
Change-Id: Iaa490842507dcc385fe7930db7347a4a99d86fdd
diff --git a/manifest.json b/manifest.json
index 7c089da..01062af 100644
--- a/manifest.json
+++ b/manifest.json
@@ -1,4 +1,4 @@
 {
   "name": "com.android.sdkext",
-  "version": 309999900
+  "version": 319999900
 }