Avoid mocking in tests for EppMetric

Followup to []  Mocking shouldn't be used when you can use the real
implementation just as easily (and more robustly) - in particular, you almost
never want to mock a value type.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=132586826

javatests/google/registry/flows/EppTestComponent.java

@@ -48,7 +48,7 @@ interface EppTestComponent {
 
     FakesAndMocksModule(FakeClock clock) {
       this.clock = clock;
-      this.metrics = mock(EppMetric.Builder.class);
+      this.metrics = new EppMetric.Builder();
       this.modulesService = mock(ModulesService.class);
       this.metricsEnqueuer = mock(BigQueryMetricsEnqueuer.class);
     }