Remove unused libbrillo-http dependency.

update_engine doesn't use libbrillo-http for anything. All the HTTP
communication is done directly using libcurl.

Bug: 27178350
TEST=Build on Brillo and Android.

Change-Id: I1267cf9ca57cd50167d703370d300de83d76a977
diff --git a/Android.mk b/Android.mk
index 45051c2..f0645d8 100644
--- a/Android.mk
+++ b/Android.mk
@@ -62,7 +62,6 @@
     system
 ue_common_shared_libraries := \
     libbrillo \
-    libbrillo-http \
     libbrillo-stream \
     libchrome