fix texts from the plugin settings

lang/en/labnbook.php

@@ -30,10 +30,10 @@ $string['view'] = 'View';
 
 // settings
 $string['labnbook_api_url'] = "LabNbook URL";
-$string['labnbook_api_url_descr'] = "The URL to the root of labnbook, with a trailing slash. E.g. https://uga.labnbook.fr/";
+$string['labnbook_api_url_descr'] = "The URL to the root of the labnbook API, with a trailing slash. E.g. https://uga.labnbook.fr/api/";
 $string['labnbook_api_key'] = "LabNbook Key";
-$string['labnbook_api_key_descr'] = "The secret key that grants Moodle access to the API of LabNbook. This key is provided by the LabNbook instance.";
-$string['labnbook_institution_id'] = "LabNbook instituion ID";
+$string['labnbook_api_key_descr'] = "The secret key that grants Moodle an access to the API of LabNbook. This key is provided by the LabNbook instance.";
+$string['labnbook_institution_id'] = "LabNbook institution ID";
 $string['labnbook_institution_id_descr'] = "The LabNbook institution ID that will be assigned to this Moodle instance.";
 
 // form