Change duration string to what it really should say

The 'duration' string is currently saying 'Duration (minutes)'.
However, the table rows on view.php and in the Moodle mobile app where this string is used push the meeting duration through format_time() which renders the duration in a nice format like '1 hour'. Thus, the 'minutes' hint is misleading and removed from the string.

lang/en/zoom.php

@@ -75,7 +75,7 @@
 $string['downloadical_desc'] = 'With this setting, you can control if a link to download an iCal file for the meeting will be shown on the activity instance overview page or not. This setting only affects the possibility to download an iCal file for third-party calendar tools. Regardless of this setting, the Zoom meeting activity will add a calendar entry into the Moodle calendar as soon as a meeting start date is set.';
 $string['downloadical_disable'] = 'Disable download iCal link';
 $string['downloadical_enable'] = 'Enable download iCal link';
-$string['duration'] = 'Duration (minutes)';
+$string['duration'] = 'Duration';
 $string['encryptiontype'] = 'Encryption type';
 $string['encryptiontype_desc'] = 'With this setting, you can control if the option to choose end-to-end encryption over enhanced encryption is shown to users in the activity instance settings or not. This setting only affects the Moodle activity instance settings. Even if you decide to always show the option, the user will still need end-to-end encryption in Zoom to finally enable end-to-end encryption.';
 $string['encryptiontype_disable'] = 'Disable encryption type chooser';