Update the BackupDatabaseForm to not persist the filename to config, as we're using config_readonly

dont-save-filename-to-config.patch

diff --git a/src/Form/BackupDatabaseForm.php b/src/Form/BackupDatabaseForm.php
index e9ba957..66851b1 100755
--- a/src/Form/BackupDatabaseForm.php
+++ b/src/Form/BackupDatabaseForm.php
@@ -70,11 +70,6 @@ class BackupDatabaseForm extends FormBase {
   public function submitForm(array &$form, FormStateInterface $form_state) {
     $values = $form_state->getValues();
 
-    // Save filename.
-    \Drupal::configFactory()->getEditable('backup_db.settings')
-      ->set('filename', $values['filename'])
-      ->save();
-
     // Call backup_db client.
     $client = \Drupal::service('backup_db.client');