Annotate RTT as @TargetApi(28).

Bug: 67596257
Test: lint tests
PiperOrigin-RevId: 185912566
Change-Id: I281fbd62865c9de150c3e2a7a3ea79c3eb85c529
diff --git a/java/com/android/incallui/call/DialerCall.java b/java/com/android/incallui/call/DialerCall.java
index cbe7c57..3788061 100644
--- a/java/com/android/incallui/call/DialerCall.java
+++ b/java/com/android/incallui/call/DialerCall.java
@@ -17,6 +17,7 @@
 package com.android.incallui.call;
 
 import android.Manifest.permission;
+import android.annotation.TargetApi;
 import android.content.Context;
 import android.hardware.camera2.CameraCharacteristics;
 import android.net.Uri;
@@ -929,6 +930,7 @@
     return getVideoTech().isTransmittingOrReceiving() || VideoProfile.isVideo(getVideoState());
   }
 
+  @TargetApi(28)
   public boolean isRttCall() {
     if (BuildCompat.isAtLeastP()) {
       return getTelecomCall().isRttActive();