Messaging: Remove compatibility for old android versions

Change-Id: Id9065d60525a509271a0e64c0e349e857cb998e2

src/com/android/messaging/datamodel/data/SelfParticipantsData.java

@@ -24,8 +24,6 @@ import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 
-import com.android.messaging.util.OsUtil;
-
 /**
  * A class that contains the list of all self participants potentially involved in a conversation.
  * This class contains both active/inactive self entries when there is multi-SIM support.
@@ -86,9 +84,6 @@ public class SelfParticipantsData {
      * Returns if a given self id represents the default self.
      */
     boolean isDefaultSelf(final String selfId) {
-        if (!OsUtil.isAtLeastL_MR1()) {
-            return true;
-        }
         final ParticipantData self = getSelfParticipantById(selfId);
         return self == null ? false : self.getSubId() == ParticipantData.DEFAULT_SELF_SUB_ID;
     }