Update metrics constant for Encryption & credentials.

Use the new metrics constant for the sub-page instead of the original
"security" metrics.

Change-Id: I0bdceae3d2e299e94791021c0d0aff2c9019fdd0
Fix: 35630998
Test: make RunSettingsRoboTests

src/com/android/settings/EncryptionAndCredential.java

@@ -67,7 +67,7 @@ public class EncryptionAndCredential extends SettingsPreferenceFragment implemen
 
     @Override
     public int getMetricsCategory() {
-        return MetricsEvent.SECURITY;
+        return MetricsEvent.ENCRYPTION_AND_CREDENTIAL;
     }
 
     @Override