Remove default public ctor from RttModifyStatus

Test: builds
Bug: 37515063
Change-Id: I1e573d945b48e28d12621078cc8f37eb076d9ee3
diff --git a/telecomm/java/android/telecom/Connection.java b/telecomm/java/android/telecom/Connection.java
index 7998359..dc0c485 100644
--- a/telecomm/java/android/telecom/Connection.java
+++ b/telecomm/java/android/telecom/Connection.java
@@ -865,6 +865,7 @@
      * {@link Call#sendRttRequest()}
      */
     public static final class RttModifyStatus {
+        private RttModifyStatus() {}
         /**
          * Session modify request was successful.
          */