Use default auth for Iceberg integration tests

Author: ahmedabu98

Diff for: .github/trigger_files/IO_Iceberg_Integration_Tests.json

@@ -1,4 +1,4 @@
 {
     "comment": "Modify this file in a trivial way to cause this test suite to run",
-    "modification": 1
+    "modification": 2
 }

Diff for: sdks/java/io/iceberg/src/test/java/org/apache/beam/sdk/io/iceberg/IcebergIOIT.java

@@ -108,8 +108,7 @@ public static void beforeClass() {
 
     catalogHadoopConf = new Configuration();
     catalogHadoopConf.set("fs.gs.project.id", options.getProject());
-    catalogHadoopConf.set(
-        "fs.gs.auth.service.account.json.keyfile", System.getenv("GOOGLE_APPLICATION_CREDENTIALS"));
+    catalogHadoopConf.set("fs.gs.auth.type", "APPLICATION_DEFAULT");
   }
 
   @Before