Fix external integ test zip dep to expect a zip (#49813)

When external plugin authors use build-tools, their integ tests depend
on the integ-test-zip artifact. However, this dependency was broken in
7.5.0 by accidentally removing the `@zip` qualifier on the maven
dependency, which works around the fact the pom for the integ-test-zip
claims the artifact is a pom instead of zip packaging. This commit
restores the workaround of using `@zip` until the pom can be fixed.

closes #49787

Author: rjernst

buildSrc/src/main/java/org/elasticsearch/gradle/DistributionDownloadPlugin.java

@@ -212,7 +212,7 @@ private Object dependencyNotation(Project project, ElasticsearchDistribution dis
         }
 
         if (distribution.getType() == Type.INTEG_TEST_ZIP) {
-            return "org.elasticsearch.distribution.integ-test-zip:elasticsearch:" + distribution.getVersion();
+            return "org.elasticsearch.distribution.integ-test-zip:elasticsearch:" + distribution.getVersion() + "@zip";
         }