chore: enable Spanner system tests in CI

Author: cy-yun

Spanner/tests/System/PgSystemTestCaseTrait.php

@@ -52,7 +52,7 @@ protected static function setUpTestDatabase(): void
             ]);
             $op->pollUntilComplete();
 
-            $db->updateDdlBatch(
+            self::$database->updateDdlBatch(
                 [
                     'CREATE TABLE IF NOT EXISTS ' . self::TEST_TABLE_NAME . ' (
                         id bigint PRIMARY KEY,
@@ -65,7 +65,7 @@ protected static function setUpTestDatabase(): void
             // Currently, the emulator doesn't support setting roles for the PG
             // dialect.
             if (!self::isEmulatorUsed()) {
-                $db->updateDdlBatch(
+                self::$database->updateDdlBatch(
                     [
                         'CREATE ROLE ' . self::DATABASE_ROLE,
                         'CREATE ROLE ' . self::RESTRICTIVE_DATABASE_ROLE,

phpunit-system.xml.dist

@@ -7,7 +7,6 @@
       <exclude>Datastore/tests/System</exclude>
       <exclude>Firestore/tests/System</exclude>
       <exclude>Logging/tests/System</exclude>
-      <exclude>Spanner/tests/System</exclude>
     </testsuite>
   </testsuites>
   <php>