Change SendEmailService to an instance field.

This allows us to inject it with Dagger and avoid using InjectRule to set it
in unit tests.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=217571475

java/google/registry/reporting/icann/IcannReportingModule.java

@@ -25,7 +25,6 @@ import dagger.Provides;
 import google.registry.bigquery.BigqueryConnection;
 import google.registry.request.HttpException.BadRequestException;
 import google.registry.request.Parameter;
-import google.registry.util.SendEmailService;
 import java.lang.annotation.Documented;
 import java.lang.annotation.Retention;
 import java.util.Optional;
@@ -115,11 +114,6 @@ public final class IcannReportingModule {
     }
   }
 
-  @Provides
-  static SendEmailService provideSendEmailService() {
-    return new SendEmailService();
-  }
-
   /** Dagger qualifier for the subdirectory we stage to/upload from. */
   @Qualifier
   @Documented