NATICK — After an online petition generated more than 1,000 signatures to stop a historic concert hall in the Clark Building downtown from being converted into office space, a Boston real estate company that owns the building has dropped the plan. Ted Davis, vice president of capital projects at Kensington Investment Company, Inc., told the Daily News Friday afternoon of the company’s decision. Davis listed several reasons for the move, including the economic fallout from COVID-19 that he said makes it unwise to invest in more office space. In November, Kensington’s architect told the Daily News of plans to convert the concert hall into office space. Amir Kripper, principal at Kripper Architecture Studio in Boston, said the work could start in three months and wrap up in this summer.