Tesla Inc. has produced more than 3 million vehicles, and a third of them have been built in China, according to Elon Musk. On Sunday, the Tesla chief executive congratulated the company’s Shanghai “gigafactory” in a twee t: “Congrats Giga Shanghai on making millionth car! Total Teslas made now over 3M.” The milestone came just a few weeks after Musk said Tesla’s factory in Fremont, Calif. , produced its 2 millionth vehicle . Tesla also has new factories in Austin, Texas, and Berlin, which Musk in June referred to as “money furnaces.” The Shanghai factory opened in 2018, but it…