deprecated class constant EXISTS_REPLACE

Applying recommended changes in src/IcsFileManager.php file.

-    if (!\Drupal::service('file.repository')->writeData($icsFileStr, $fileUri, FileSystemInterface::EXISTS_REPLACE)) {
+    if (!\Drupal::service('file.repository')->writeData($icsFileStr, $fileUri, FileExists::Replace)) {
       $this->handleFileSaveError($fileUri);

-      $file = \Drupal::service('file.repository')->writeData($icsFileStr, $fileUri, FileSystemInterface::EXISTS_REPLACE);
+      $file = \Drupal::service('file.repository')->writeData($icsFileStr, $fileUri, FileExists::Replace);

This is also fixed in 📌 Automated Drupal 11 compatibility fixes for ics_field Needs review .