Explicitly export content providers

In a future version of Android, the default value for
<provider android:exported> will change from true to false.
Explicitly set android:exported="true"

Bug: 3306452
Change-Id: I4df74c627505c596a3bce81a5417d32e5002a75f
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index cfe0e18..c73d92f 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -53,6 +53,7 @@
         <uses-library android:name="javax.obex" />
         <provider android:name=".opp.BluetoothOppProvider"
             android:authorities="com.android.bluetooth.opp"
+            android:exported="true"
             android:process="@string/process">
             <path-permission
                     android:path="/btopp"