Revert "Hide Files app launcher icon."

This reverts commit 24e4604595.

Un-hiding this for continued development in nyc-dev.

Based on conversations between those at higher paygrades, we'll either leave this visible or re-hide prior to next dev release.

Change-Id: I235eb0f593daa7b34ea10ed4c9df4eaa6c68078c

packages/DocumentsUI/AndroidManifest.xml

@@ -58,6 +58,7 @@
             android:label="@string/files_label">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
         </activity>