Remove Preconditions usage in TestNetworkSpecifier

Preconditions is a hidden API utility. It can be easily replace by
inline checks.

Bug: 177046265
Test: m
Change-Id: I3f722075fb9c74e12e40348ba4faad2f0fa67178
diff --git a/framework/src/android/net/TestNetworkSpecifier.java b/framework/src/android/net/TestNetworkSpecifier.java
index b7470a5..117457d 100644
--- a/framework/src/android/net/TestNetworkSpecifier.java
+++ b/framework/src/android/net/TestNetworkSpecifier.java
@@ -23,8 +23,6 @@
 import android.os.Parcelable;
 import android.text.TextUtils;
 
-import com.android.internal.util.Preconditions;
-
 import java.util.Objects;
 
 /**
@@ -43,7 +41,9 @@
     private final String mInterfaceName;
 
     public TestNetworkSpecifier(@NonNull String interfaceName) {
-        Preconditions.checkStringNotEmpty(interfaceName);
+        if (TextUtils.isEmpty(interfaceName)) {
+            throw new IllegalArgumentException("Empty interfaceName");
+        }
         mInterfaceName = interfaceName;
     }