AOSP/Messaging - Update language to comply with Android's inclusive language guidance.

See https://source.android.com/setup/contribute/respectful-code for reference

BUG=161896447

Test: make and make messagingtests
Change-Id: I01c520f1d5e9eab8dbb25b08d133ae34bd301093

src/com/android/messaging/ui/appsettings/ApnEditorActivity.java

@@ -365,8 +365,8 @@ public class ApnEditorActivity extends BugleActionBarActivity {
                 protected Void doInBackground(Void... params) {
                     ContentValues values = new ContentValues();
 
-                    // Add a dummy name "Untitled", if the user exits the screen without adding a
-                    // name but entered other information worth keeping.
+                    // Add a placeholder name "Untitled", if the user exits the screen without
+                    // adding a name but entered other information worth keeping.
                     values.put(Telephony.Carriers.NAME, name.length() < 1 ?
                             getResources().getString(R.string.untitled_apn) : name);
                     values.put(Telephony.Carriers.MMSPROXY, checkNotSet(mMmsProxy.getText()));