[8.7] Fix Azure third party tests configuration (#95461) (#95466)

Backports #95461 to 8.7

> Adjust the system property used to determine whether or not a fixture
> should be used.

Co-authored-by: Francisco Fernández Castaño <[email protected]>

Author: arteam

modules/repository-azure/src/internalClusterTest/java/org/elasticsearch/repositories/azure/AzureStorageCleanupThirdPartyTests.java

@@ -40,7 +40,7 @@
 import static org.hamcrest.Matchers.not;
 
 public class AzureStorageCleanupThirdPartyTests extends AbstractThirdPartyRepositoryTestCase {
-    private static final boolean USE_FIXTURE = Booleans.parseBoolean(System.getProperty("azure_use_fixture", "true"));
+    private static final boolean USE_FIXTURE = Booleans.parseBoolean(System.getProperty("test.azure.fixture", "true"));
 
     @ClassRule
     public static AzureHttpFixture fixture = new AzureHttpFixture(