Fix deprecation warning in build script (#11642)

Author: laurit

conventions/src/main/kotlin/otel.java-conventions.gradle.kts

@@ -294,8 +294,12 @@ tasks {
   withType<AbstractArchiveTask>().configureEach {
     isPreserveFileTimestamps = false
     isReproducibleFileOrder = true
-    dirMode = Integer.parseInt("0755", 8)
-    fileMode = Integer.parseInt("0644", 8)
+    dirPermissions {
+      unix("755")
+    }
+    filePermissions {
+      unix("644")
+    }
   }
 
   // Convenient when updating errorprone