Replace `getTableName` to work on resource, not on connection object

[jakwinkler]

Code change required:

    $connection = $this->resourceConnection->getConnection();

    $select = $connection->select()->from(['layout_update' => $connection->getTableName('layout_update')],

$connection->getTableName() does not work with table prefixes

it needs to use resourceConnection object to get a proper tableName using table prefix

$this->resourceConnection->getTableName('layout_update')],