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/ClearViewsCommandTest.php

@@ -1,6 +1,7 @@
 <?php namespace Tests\Commands;
 
 use BookStack\Entities\Models\Page;
+use Illuminate\Support\Facades\DB;
 use Tests\TestCase;
 
 class ClearViewsCommandTest extends TestCase
@@ -19,7 +20,9 @@ class ClearViewsCommandTest extends TestCase
             'views' => 1
         ]);
 
+        DB::rollBack();
         $exitCode = \Artisan::call('bookstack:clear-views');
+        DB::beginTransaction();
         $this->assertTrue($exitCode === 0, 'Command executed successfully');
 
         $this->assertDatabaseMissing('views', [