Add type declaration in stub

Author: adoy

ext/oci8/oci8.stub.php

@@ -552,7 +552,7 @@ function oci_unregister_taf_callback($connection): bool {}
 
 class OCILob {
     /** @var resource */
-    public readonly $descriptor;
+    public readonly mixed $descriptor;
 
     /**
      * @alias oci_lob_save
@@ -683,7 +683,7 @@ public function free(): bool {}
 
 class OCICollection {
     /** @var resource */
-    public readonly $collection;
+    public readonly mixed $collection;
     /**
      * @alias oci_free_collection
      * @tentative-return-type