Remove targetSdkVersion from AndroidManifest.xml

Bug: 27350753

The build system will inject the correct targetSdkVersion.

Change-Id: I4473336d02d1421c19c425899af1fd7b8b2af767
(cherry picked from commit c45787fae0a3e016c2b1cc87042266d323a9a3f6)

AndroidManifest.xml

@@ -22,7 +22,7 @@
     <original-package android:name="com.android.alarmclock" />
     <original-package android:name="com.android.deskclock" />
 
-    <uses-sdk android:minSdkVersion="19" android:targetSdkVersion="24" />
+    <uses-sdk android:minSdkVersion="19" />
 
     <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
     <uses-permission android:name="android.permission.WAKE_LOCK"/>