State the locations of all Pet Services business.
location refers to city; Pet Services business refers to category_name = 'Pet Services'
SELECT T1.city FROM Business AS T1 INNER JOIN Business_Categories AS T2 ON T1.business_id = T2.business_id INNER JOIN Categories AS T3 ON T2.category_id = T3.category_id WHERE T3.category_name = 'Pet Services'