remove misleading fileno method from NpipeFileIOBase class

the underlying method used was removed in version 3.6.0, commit 2b2d711

Signed-off-by: Lev Blit <[email protected]>

Author: lev-blit

docker/transport/npipesocket.py

@@ -211,9 +211,6 @@ def close(self):
         super().close()
         self.sock = None
 
-    def fileno(self):
-        return self.sock.fileno()
-
     def isatty(self):
         return False