OAKLAND — Twitter has scrapped plans to open a downtown Oakland office and will slash its footprint in San Francisco and several other cities, as well as completely exit other cities, the social media giant said Wednesday. In 2021, Twitter sketched out plans to lease a large chunk of office space in downtown Oakland, saying at the time that the East Bay location would be a model for the company’s emerging hybrid workplace model. Now, Twitter is outlining space cutbacks in at least a dozen locations, including San Francisco and the East Bay. “We will also no longer move forward with plans to op…