Update signature of Entity::markFieldUpdated

[nickvergessen]

Ref nextcloud/server@e91457d

Summary

PHP Fatal error:  Declaration of OCA\Deck\Db\RelationalEntity::markFieldUpdated($attribute) must be compatible with OCP\AppFramework\Db\Entity::markFieldUpdated(string $attribute): void in /var/www/html/apps/deck/lib/Db/RelationalEntity.php on line 56
PHP Fatal error:  Declaration of OCA\Deck\Db\RelationalEntity::markFieldUpdated($attribute) must be compatible with OCP\AppFramework\Db\Entity::markFieldUpdated(string $attribute): void in /var/www/html/apps/deck/lib/Db/RelationalEntity.php on line 56
PHP Fatal error:  Declaration of OCA\Deck\Db\RelationalEntity::markFieldUpdated($attribute) must be compatible with OCP\AppFramework\Db\Entity::markFieldUpdated(string $attribute): void in /var/www/html/apps/deck/lib/Db/RelationalEntity.php on line 56

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Documentation (manuals or wiki) has been updated or is not required

[tobiasKaminsky]

Works with latest master

[nickvergessen]

7.4 will be fixed in #4389