Remove libbluetooth-system requirement.

This module doesn't exist and it being missing was
silently ignored.

Bug: 7456955
Test: no longer receive an error for this.
Change-Id: Ib84b592d25e19b2c6b0d20466015553fe57f5bf8
diff --git a/service/Android.bp b/service/Android.bp
index 89bd447..91fab48 100644
--- a/service/Android.bp
+++ b/service/Android.bp
@@ -71,7 +71,6 @@
     btserviceLinuxSrc +
     btserviceDaemonSrc +
     ["main.cc"],
-    required: ["libbluetooth-system"],
     static_libs: [
         "libbluetooth-binder-common",
         "libbtcore",