Use LauncherActivity name from Nougat.

So launcher doesn't disappear on upgrade.

Bug: 62836700
Test: Build install test with different names.
Change-Id: I53e93e6d84f6c289d10b46f5a32b74f56453169c
(cherry picked from commit e2b5ffee1b2863a19ec8f9eb2c48bd81a2dcf7a4)
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index ef3871c..9aa9a79 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -58,7 +58,7 @@
 
         <!--  Preserve original launcher activity from Nougat. -->
         <activity-alias
-            android:name=".Launcher"
+            android:name=".LauncherActivity"
             android:targetActivity=".files.LauncherActivity"
             android:label="@string/launcher_label"
             android:icon="@drawable/launcher_icon" >