ISTWCMS-4535 Change assertNoFieldByName() to assertSession()->buttonNotExists()

Change record:
https://www.drupal.org/node/3129738

tests/src/Functional/UwWcmsBasicTest.php

@@ -1748,7 +1748,7 @@ class UwWcmsBasicTest extends BrowserTestBase {
     $this->clickLink('Add block');
     $this->clickLink('Facts and figures');
     // The top-level remove button doesn't exist.
-    $this->assertNoFieldByName('settings_block_form_field_uw_ff_fact_figure_0_remove');
+    $this->assertSession()->buttonNotExists('settings_block_form_field_uw_ff_fact_figure_0_remove');
     // Check 'Default background colour' field help text.
     $this->assertSession()->pageTextContains('When gold is selected, the default colour will always be black.');
     // Check 'Default background colour' field default value.