Remove the use of InjectRule in UrlFetchUtilsTest

Random used to be a static variable which requires InjectRule to mock it in unit tests. It is now a singleton, which ensures that the same instance is called every time and Random.nextBytes() generates results that distribute uniformly between each call.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=217592767

javatests/google/registry/tmch/NordnUploadActionTest.java

@@ -14,6 +14,7 @@
 
 package google.registry.tmch;
 
+import static com.google.common.base.Randoms.insecureRandom;
 import static com.google.common.net.HttpHeaders.AUTHORIZATION;
 import static com.google.common.net.HttpHeaders.CONTENT_TYPE;
 import static com.google.common.net.HttpHeaders.LOCATION;
@@ -115,6 +116,7 @@ public class NordnUploadActionTest {
     action.taskQueueUtils = new TaskQueueUtils(new Retrier(new FakeSleeper(clock), 3));
     action.tld = "tld";
     action.tmchMarksdbUrl = "http://127.0.0.1";
+    action.random = insecureRandom();
   }
 
   @Test