Issue #3274842: Remove unnecessary brackets from $this->moduleHandler

Fixes issue from 686fd3b4.

src/Controller/HandlePdfController.php

@@ -171,7 +171,7 @@ class HandlePdfController extends ControllerBase {
    *   The FillPDF context to alter.
    */
   public function alterContext(array &$context): void {
-    $this->moduleHandler()->alter('fillpdf_populate_pdf_context', $context);
+    $this->moduleHandler->alter('fillpdf_populate_pdf_context', $context);
   }
 
   /**