MDL-58064 lang: Clarify the PHP 7.x limitations

These are related to SQL*Server support only and affect all PHP 7
versions, not just 7.0.x. Credit goes to Eloy Lafuente for spotting
this.

lang/en/install.php

@@ -219,7 +219,7 @@
 $string['pgsqlextensionisnotpresentinphp'] = 'PHP has not been properly configured with the PGSQL extension so that it can communicate with PostgreSQL.  Please check your php.ini file or recompile PHP.';
 $string['phpextension'] = '{$a} PHP extension';
 $string['phpversion'] = 'PHP version';
-$string['phpversionhelp'] = '<p>Moodle requires a PHP version of at least 5.6.5 or 7.1 (7.0.x has some engine limitations).</p>
+$string['phpversionhelp'] = '<p>Moodle requires a PHP version of at least 5.6.5 (7.x has some engine limitations).</p>
 <p>You are currently running version {$a}.</p>
 <p>You must upgrade PHP or move to a host with a newer version of PHP.</p>';
 $string['releasenoteslink'] = 'For information about this version of Moodle, please see the release notes at {$a}';