Fix targetSdkVersion for NetworkStack

targetSdkVersion was set to 28 in aosp/916713, however this was broken
by the manifest refactor in aosp/923338: the targetSdk is not preserved
in the manifest merge.

Test: aapt dump badging shows targetSdkVersion 28
Change-Id: I7d06b141856e96ef011db32094bfc62a8cd1b350

packages/NetworkStack/AndroidManifest.xml

@@ -19,6 +19,7 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
           package="com.android.networkstack"
           android:sharedUserId="android.uid.networkstack">
+    <uses-sdk android:minSdkVersion="28" android:targetSdkVersion="28" />
     <!-- Signature permission defined in NetworkStackStub -->
     <uses-permission android:name="android.permission.MAINLINE_NETWORK_STACK" />
     <application>
@@ -28,4 +29,4 @@
             </intent-filter>
         </service>
     </application>
-</manifest>
+</manifest>

packages/NetworkStack/AndroidManifestBase.xml

@@ -20,7 +20,6 @@
           package="com.android.networkstack"
           android:versionCode="11"
           android:versionName="Q-initial">
-    <uses-sdk android:minSdkVersion="28" android:targetSdkVersion="28" />
     <uses-permission android:name="android.permission.INTERNET" />
     <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

packages/NetworkStack/AndroidManifest_InProcess.xml

@@ -20,6 +20,7 @@
           package="com.android.networkstack.inprocess"
           android:sharedUserId="android.uid.system"
           android:process="system">
+    <uses-sdk android:minSdkVersion="28" android:targetSdkVersion="28" />
     <application>
         <service android:name="com.android.server.NetworkStackService" android:process="system">
             <intent-filter>
@@ -27,4 +28,4 @@
             </intent-filter>
         </service>
     </application>
-</manifest>
+</manifest>