Just had a look at the file in question you are indeed correct about it being a typo. I would not recommend you alter the file to fix this, as this would break with future upgrade path and also it looks as if they are looking to fix this functionality in the process.
/**
* Retrieve minimum query length
*
* @deprecated after 1.3.2.3 use getMinQueryLength() instead
* @return int
*/
public function getMinQueryLenght()
{
return Mage::getStoreConfig(self::XML_PATH_MIN_QUERY_LENGTH, $this->getStoreId());
}
/**
* Retrieve minimum query length
*
* @return int
*/
public function getMinQueryLength(){
return $this->getMinQueryLenght();
}