Set NetworkStack targetSdk to 28

Test: flashed, booted, WiFi works
Change-Id: I7bbd7eb563432a290358d16652c0ae69e9772002
diff --git a/packages/NetworkStackPermissionStub/AndroidManifest.xml b/packages/NetworkStackPermissionStub/AndroidManifest.xml
index ba8a178..62bf3de 100644
--- a/packages/NetworkStackPermissionStub/AndroidManifest.xml
+++ b/packages/NetworkStackPermissionStub/AndroidManifest.xml
@@ -21,6 +21,7 @@
     android:sharedUserId="android.uid.networkstack"
     android:versionCode="10"
     android:versionName="Q-initial">
+    <uses-sdk android:minSdkVersion="28" android:targetSdkVersion="28" />
     <!--
     This package only exists to define the below permissions, and enforce that they are only
     granted to apps sharing the same signature.
@@ -36,4 +37,4 @@
                 android:protectionLevel="signature"/>
 
     <application android:name="com.android.server.NetworkStackPermissionStub"/>
-</manifest>
\ No newline at end of file
+</manifest>