==== Background
The `temporary-account-viewer` is configured to be restricted to users that meet requirements for edit count and account age: https://gerrit.wikimedia.org/r/c/operations/mediawiki-config/+/1148827
This was done quickly, and using custom code that was not easily re-usable for other groups that might have requirements.
After T409714, a group can be configured more easily using `$wgRestrictedGroups`. The `temporary-account-viewer` group should use this config instead.
Existing config, to be removed ([[ https://gerrit.wikimedia.org/g/operations/mediawiki-config/+/1e24b2c1a18e87d8d09aa98ccc22c24b0090edef/wmf-config/CommonSettings.php#4410 | codesearch ]]):
```lang=php
$wgCheckUserGroupRequirements = [
'temporary-account-viewer' => [
'edits' => 300,
'age' => 86400 * 30 * 6,
'exemptGroups' => [ 'steward' ],
'reason' => 'checkuser-group-requirements-temporary-account-viewer',
],
];
```
New config:
```lang=php
$wgRestrictedGroups['temporary-account-viewer'] = [
'memberConditions' => [
'&',
[ APCOND_EDITCOUNT, 300 ],
[ APCOND_AGE, 86400 * 30 * 6 ],
],
'canBeIgnored' => true,
];
```
Notes:
* Instead of `exemptGroups`, we should set `canBeIgnored` true and assign `ignore-restricted-groups` to stewards
* We may need to change the message key for the reason, depending on how that is handled in T409714
==== Acceptance criteria
* `temporary-account-viewer` is configured using `$wgRestrictedGroups` instead of `$wgCheckUserGroupRequirements`
* `ignore-restricted-groups` permission is assigned to stewards
* There is no functional difference
* It is possible to remove `$wgCheckUserGroupRequirements` and related code
(`$wgCheckUserGroupRequirements` is not actually removed in this task.)