Make some 'notification sound' strings consistent with the rest

Closes #4324
// FREEBIE

res/values/strings.xml

@@ -674,7 +674,7 @@
     <!-- recipient_preferences -->
     <string name="recipient_preferences__mute_conversation">Mute conversation</string>
     <string name="recipient_preferences__disable_notifications_for_this_conversation">Disable notifications for this conversation</string>
-    <string name="recipient_preferences__notification_tone">Notification tone</string>
+    <string name="recipient_preferences__notification_sound">Notification sound</string>
     <string name="recipient_preferences__vibrate">Vibrate</string>
     <string name="recipient_preferences__block">Block</string>
     <string name="recipient_preferences__color">Color</string>

res/xml/recipient_preferences.xml

@@ -12,7 +12,7 @@
     <org.thoughtcrime.securesms.preferences.AdvancedRingtonePreference
                         android:dependency="pref_key_recipient_mute"
                         android:key="pref_key_recipient_ringtone"
-                        android:title="@string/recipient_preferences__notification_tone"
+                        android:title="@string/recipient_preferences__notification_sound"
                         android:ringtoneType="notification"
                         android:showSilent="false"
                         android:showDefault="true"