java: Remove an unecessary include from settings.gradle

We don't have an app directory and Android Studio is happy with an empty file.
Removing the file does make the Android Studio complain that the Gradle build
is not as expected.

Change-Id: Ide49786dbc3b36a35bf5e11664ec22c53288c122
diff --git a/syncbase/settings.gradle b/syncbase/settings.gradle
index e7b4def..e69de29 100644
--- a/syncbase/settings.gradle
+++ b/syncbase/settings.gradle
@@ -1 +0,0 @@
-include ':app'