Build/Test Tools: Remove Unicode character from PHPUnit version check message.

Not all CLI tools can handle Unicode characters or non-system specific line endings well, so this type of CLI messaging should always be written with the optimal cross-platform, cross-CLI tool end-user experience in mind.

Follow-up to [51581].

Props jrf.
See #53363.

git-svn-id: https://develop.svn.wordpress.org/trunk@51584 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

tests/phpunit/includes/bootstrap.php

@@ -39,7 +39,7 @@
 
 if ( version_compare( $phpunit_version, '5.7.21', '<' ) ) {
 	printf(
-		'Error: Looks like you’re using PHPUnit %s. WordPress requires at least PHPUnit 5.7.21.' . PHP_EOL,
+		"Error: Looks like you're using PHPUnit %s. WordPress requires at least PHPUnit 5.7.21." . PHP_EOL,
 		$phpunit_version
 	);
 	echo 'Please use the latest PHPUnit version supported for the PHP version you are running the tests on.' . PHP_EOL;