Fix Type Annotation in pandas/core/api.py
Part of #25882 

Current errors are:

    pandas\core\api.py:5: error: Module 'pandas.core.arrays.integer' has no attribute 'Int8Dtype'
    pandas\core\api.py:5: error: Module 'pandas.core.arrays.integer' has no attribute 'Int16Dtype'
    pandas\core\api.py:5: error: Module 'pandas.core.arrays.integer' has no attribute 'Int32Dtype'
    pandas\core\api.py:5: error: Module 'pandas.core.arrays.integer' has no attribute 'Int64Dtype'
    pandas\core\api.py:5: error: Module 'pandas.core.arrays.integer' has no attribute 'UInt8Dtype'
    pandas\core\api.py:5: error: Module 'pandas.core.arrays.integer' has no attribute 'UInt16Dtype'
    pandas\core\api.py:5: error: Module 'pandas.core.arrays.integer' has no attribute 'UInt32Dtype'
    pandas\core\api.py:5: error: Module 'pandas.core.arrays.integer' has no attribute 'UInt64Dtype'
