Tests: Correct some @covers tags in wp_html_split() and wptexturize() tests.

As `preg_split()` is not a user-defined function, it causes notices when generating the code coverage report:
{{{
"@covers ::preg_split" is invalid
}}}

Instead, it appears that the intention was to test the performance of these WordPress functions:

* `get_html_split_regex()`
* `_get_wptexturize_split_regex()`
* `_get_wptexturize_shortcode_regex()`

Follow-up to [34761], [53562].

See #39265, #55652.

git-svn-id: https://develop.svn.wordpress.org/trunk@54051 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/tests/formatting/wpHtmlSplit.php

@@ -42,7 +42,7 @@ class Tests_Formatting_wpHtmlSplit extends WP_UnitTestCase {
 	 *
 	 * @dataProvider data_whole_posts
 	 *
-	 * @covers ::preg_split
+	 * @covers ::get_html_split_regex
 	 */
 	public function test_pcre_performance( $input ) {
 		$regex  = get_html_split_regex();

tests/phpunit/tests/formatting/wpTexturize.php

@@ -2174,7 +2174,8 @@ String with a number followed by a single quote !q1!Expendables 3!q1! vestibulum
 	 *
 	 * @dataProvider data_whole_posts
 	 *
-	 * @covers ::preg_split
+	 * @covers ::_get_wptexturize_split_regex
+	 * @covers ::_get_wptexturize_shortcode_regex
 	 */
 	public function test_pcre_performance( $input ) {
 		global $shortcode_tags;