Add @hide to RttAudioMode IntDef

IntDefs apparently require an @hide annotation to avoid breaking CTS
tests. Adding it here.

Change-Id: Ifd748b55e68091132571df7e74fdb797bd6a83fc
Test: CTS
Fix: 35808951
diff --git a/api/current.txt b/api/current.txt
index 5555d1f..159b025 100644
--- a/api/current.txt
+++ b/api/current.txt
@@ -36694,9 +36694,6 @@
     field public static final int RTT_MODE_VCO = 3; // 0x3
   }
 
-  public static abstract class Call.RttCall.RttAudioMode implements java.lang.annotation.Annotation {
-  }
-
   public final class CallAudioState implements android.os.Parcelable {
     ctor public CallAudioState(boolean, int, int);
     method public static java.lang.String audioRouteToString(int);
diff --git a/api/system-current.txt b/api/system-current.txt
index 701c86f..deeb679 100644
--- a/api/system-current.txt
+++ b/api/system-current.txt
@@ -39667,9 +39667,6 @@
     field public static final int RTT_MODE_VCO = 3; // 0x3
   }
 
-  public static abstract class Call.RttCall.RttAudioMode implements java.lang.annotation.Annotation {
-  }
-
   public final class CallAudioState implements android.os.Parcelable {
     ctor public CallAudioState(boolean, int, int);
     method public static java.lang.String audioRouteToString(int);
diff --git a/api/test-current.txt b/api/test-current.txt
index 1979667..694415f 100644
--- a/api/test-current.txt
+++ b/api/test-current.txt
@@ -36776,9 +36776,6 @@
     field public static final int RTT_MODE_VCO = 3; // 0x3
   }
 
-  public static abstract class Call.RttCall.RttAudioMode implements java.lang.annotation.Annotation {
-  }
-
   public final class CallAudioState implements android.os.Parcelable {
     ctor public CallAudioState(boolean, int, int);
     method public static java.lang.String audioRouteToString(int);
diff --git a/telecomm/java/android/telecom/Call.java b/telecomm/java/android/telecom/Call.java
index d67a0d6..1507082 100644
--- a/telecomm/java/android/telecom/Call.java
+++ b/telecomm/java/android/telecom/Call.java
@@ -871,6 +871,7 @@
      * party, if it is active.
      */
     public static final class RttCall {
+        /** @hide */
         @Retention(RetentionPolicy.SOURCE)
         @IntDef({RTT_MODE_INVALID, RTT_MODE_FULL, RTT_MODE_HCO, RTT_MODE_VCO})
         public @interface RttAudioMode {}