Fix strict type errors: Convert FormattableMarkup to strings (simple replacement) in core Functional tests

Closes #3404273

core/modules/block_content/tests/src/Functional/BlockContentRevisionsTest.php

@@ -2,7 +2,6 @@
 
 namespace Drupal\Tests\block_content\Functional;
 
-use Drupal\Component\Render\FormattableMarkup;
 use Drupal\block_content\Entity\BlockContent;
 use Drupal\user\UserInterface;
 
@@ -76,7 +75,7 @@ public function testRevisions() {
         ->getStorage('block_content')
         ->loadRevision($revision_id);
       // Verify revision log is the same.
-      $this->assertEquals($logs[$delta], $loaded->getRevisionLogMessage(), new FormattableMarkup('Correct log message found for revision @revision', ['@revision' => $loaded->getRevisionId()]));
+      $this->assertEquals($logs[$delta], $loaded->getRevisionLogMessage(), "Correct log message found for revision $revision_id");
       if ($delta > 0) {
         $this->assertInstanceOf(UserInterface::class, $loaded->getRevisionUser());
         $this->assertIsNumeric($loaded->getRevisionUserId());