vibrator: enable vintf java

So constants can be used from Java.

Bug: 136027762
Test: compile
Change-Id: I3381703b80ec168688a67cf9c07d598ce881be55
diff --git a/vibrator/aidl/Android.bp b/vibrator/aidl/Android.bp
index 18468ef..cd5439f 100644
--- a/vibrator/aidl/Android.bp
+++ b/vibrator/aidl/Android.bp
@@ -5,10 +5,5 @@
         "android/hardware/vibrator/*.aidl",
     ],
     stability: "vintf",
-    backend: {
-        java: {
-            enabled: false,
-        },
-    },
 }