gh-62184: Remove _pyio import of _io.FileIO

This was added in the add of `_io`, isn't used since bpo-21859 when a
`_pyio` implementation was added which defines `FileIO` lower down in
the file.

Author: cmaloney

Lib/_pyio.py

@@ -645,8 +645,6 @@ def write(self, b):
         self._unsupported("write")
 
 io.RawIOBase.register(RawIOBase)
-from _io import FileIO
-RawIOBase.register(FileIO)
 
 
 class BufferedIOBase(IOBase):