Remove Tethering @TestApi

Modules shouldn't have TestApis, as documented in go/android-api-types.
Additionally, nothing depends on these TestApis existing.

Bug: 170395679
Test: m checkapi
Change-Id: I6e2c8298e90b4b54f0264be974d036fa08cd5632
Merged-In: I6e2c8298e90b4b54f0264be974d036fa08cd5632

Tethering/common/TetheringLib/src/android/net/TetheredClient.java

@@ -19,7 +19,6 @@ package android.net;
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.SystemApi;
-import android.annotation.TestApi;
 import android.os.Parcel;
 import android.os.Parcelable;
 
@@ -34,7 +33,6 @@ import java.util.Objects;
  * @hide
  */
 @SystemApi
-@TestApi
 public final class TetheredClient implements Parcelable {
     @NonNull
     private final MacAddress mMacAddress;

Tethering/common/TetheringLib/src/android/net/TetheringManager.java

@@ -23,7 +23,6 @@ import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.RequiresPermission;
 import android.annotation.SystemApi;
-import android.annotation.TestApi;
 import android.content.Context;
 import android.os.Bundle;
 import android.os.ConditionVariable;
@@ -55,7 +54,6 @@ import java.util.function.Supplier;
  * @hide
  */
 @SystemApi
-@TestApi
 public class TetheringManager {
     private static final String TAG = TetheringManager.class.getSimpleName();
     private static final int DEFAULT_TIMEOUT_MS = 60_000;