Fix some unit tests

- some proguard flags were stale
- some deprecated methods were legitimately stripped - kill the tests
for them

Bug: 4330508
Change-Id: I6d5c46c99d002895377f32b203844e9a6dcf0074
diff --git a/proguard.flags b/proguard.flags
index 0f6c90a..b39a182 100644
--- a/proguard.flags
+++ b/proguard.flags
@@ -192,6 +192,10 @@
   *** getBody();
 }
 
+-keepclasseswithmembers class com.android.email.mail.FolderProperties {
+  *** getDisplayName(int);
+}
+
 # The following classes are used only by unit tests.
 # We should move them into tests/ if possible.