Declare explicitly the platformproto dependency

Do not depend on the harness transitive dependencies.

Change-Id: I599c483fcfcfb08ca95ff3644dbeb8aedaa06f54
Test: presubmit
Bug: 191784513
diff --git a/hostsidetests/systemui/Android.bp b/hostsidetests/systemui/Android.bp
index 6de52cd..6fd9c8c 100644
--- a/hostsidetests/systemui/Android.bp
+++ b/hostsidetests/systemui/Android.bp
@@ -29,6 +29,7 @@
 
     static_libs: [
         "cts-statsd-atom-host-test-utils",
+        "platformprotos",
     ],
     // Tag this module as a cts test artifact
     test_suites: [