Performed fixes for failing tests on php8

- Commands that run a truncate DB action failed due to messing up the
  test transations so we mnaully work around that now to ensure a
transaction exists for the test to cleanup afterwards.
- Updated dompdf lib version

tests/Commands/RegeneratePermissionsCommandTest.php

@@ -2,12 +2,14 @@
 
 use BookStack\Auth\Permissions\JointPermission;
 use BookStack\Entities\Models\Page;
+use Illuminate\Support\Facades\DB;
 use Tests\TestCase;
 
 class RegeneratePermissionsCommandTest extends TestCase
 {
     public function test_regen_permissions_command()
     {
+        \DB::rollBack();
         JointPermission::query()->truncate();
         $page = Page::first();
 
@@ -15,6 +17,7 @@ class RegeneratePermissionsCommandTest extends TestCase
 
         $exitCode = \Artisan::call('bookstack:regenerate-permissions');
         $this->assertTrue($exitCode === 0, 'Command executed successfully');
+        DB::beginTransaction();
 
         $this->assertDatabaseHas('joint_permissions', ['entity_id' => $page->id]);
     }