fix: small grammatical issue for default description

In speaking, we use a /ə/ before a consonant sound.

Resolves #330

lang/en/auth_outage.php

@@ -89,7 +89,7 @@
 $string['defaulttitlevalue'] = 'System down from {{start}} for {{duration}}';
 $string['defaultdescription'] = 'Description';
 $string['defaultdescriptiondescription'] = 'Default warning message for outages. Use {{start}} and {{stop}} placeholders as required.';
-$string['defaultdescriptionvalue'] = 'There is an scheduled maintenance from {{start}} to {{stop}} and our system will not be available during that time.';
+$string['defaultdescriptionvalue'] = 'There is maintenance scheduled from {{start}} to {{stop}} and our system will not be available during that time.';
 $string['description'] = 'Public Description';
 $string['description_help'] = 'A full description of the outage, publicly visible by all users.';
 $string['finish'] = 'Finish';