Update engine now depends on otacerts

The otacerts.zip is aleady added to the system/recovery image. Add the
dependency here anyway. Also drop the dependency on
update_engine_payload_key.

Bug: 116660991
Test: build and apply an update
Change-Id: I0353af86c4e66eec9ce84901ac09fb78bd924116
diff --git a/Android.bp b/Android.bp
index a691e7e..a7f9215 100644
--- a/Android.bp
+++ b/Android.bp
@@ -306,7 +306,7 @@
     static_libs: ["libupdate_engine_android"],
     required: [
         "cacerts_google",
-        "update_engine_payload_key",
+        "otacerts",
     ],
 
     srcs: ["main.cc"],
@@ -380,7 +380,7 @@
     },
 
     required: [
-        "update_engine_payload_key.recovery",
+        "otacerts.recovery",
     ],
 }