Build/Test Tools: Continue eliminating randomness in tests.

See #37371


git-svn-id: https://develop.svn.wordpress.org/trunk@38938 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/tests/post/wpUniquePostSlug.php

@@ -27,7 +27,7 @@ class Tests_Post_WpUniquePostSlug extends WP_UnitTestCase {
 				$post = array(
 					'post_author' => $author_id,
 					'post_status' => 'publish',
-					'post_content' => rand_str(),
+					'post_content' => 'Post content',
 					'post_title' => $post_title,
 				);