Less spammy ProGuard.

Change-Id: I465921b878c4ed6ec5d564704801e435d1aaa63c
diff --git a/core/proguard_basic_keeps.flags b/core/proguard_basic_keeps.flags
index 622d4ee..4a85db0 100644
--- a/core/proguard_basic_keeps.flags
+++ b/core/proguard_basic_keeps.flags
@@ -59,3 +59,6 @@
 # platform version.  We know about them, and they are safe.
 # See proguard-android.txt in the SDK package.
 -dontwarn android.support.**
+
+# Less spammy.
+-dontnote