run a civix upgrade to support PHP >= 8.0

Using versions of this extension that are previous to this PR with PHP versions >= 7.4 and < 8.0 caused this warning:

[PHP Deprecation] Array and string offset access syntax with curly braces is deprecated at /com.ixiam.modules.optionsimporter/optionsimporter.civix.php:246

But from PHP 8.0 that syntax causes an error rather than a warning.

In order to fix that, as the issue was in the .civix.php file, I executed a civix upgrade. All the changes in this PR come from what that upgrade did.