Remove assert for R+

Mainline only ships to R+ devices, so this assertion is guaranteed to be
true.

Change-Id: I1fbc0a50dc35a306d782a0219955c51954deeca7
Test: TH
diff --git a/staticlibs/testutils/devicetests/com/android/testutils/TestNetworkTracker.kt b/staticlibs/testutils/devicetests/com/android/testutils/TestNetworkTracker.kt
index 84fb47b..341d55f 100644
--- a/staticlibs/testutils/devicetests/com/android/testutils/TestNetworkTracker.kt
+++ b/staticlibs/testutils/devicetests/com/android/testutils/TestNetworkTracker.kt
@@ -29,7 +29,6 @@
 import android.os.Binder
 import android.os.Build
 import androidx.annotation.RequiresApi
-import com.android.modules.utils.build.SdkLevel.isAtLeastR
 import com.android.modules.utils.build.SdkLevel.isAtLeastS
 import java.util.concurrent.CompletableFuture
 import java.util.concurrent.TimeUnit
@@ -137,7 +136,6 @@
 
         network = try {
             if (lp != null) {
-                assertTrue(isAtLeastR(), "Cannot specify TestNetwork LinkProperties before R")
                 tnm.setupTestNetwork(lp, true /* isMetered */, binder)
             } else {
                 tnm.setupTestNetwork(iface.interfaceName, binder)