【fluid clean】remove fluid.dygraph.rnn.lstmcell and fluid.dygraph.rnn.grucell (#48719)

Author: lugimzzz

python/paddle/fluid/dygraph/__init__.py

@@ -43,9 +43,6 @@
 from . import static_runner
 from .static_runner import StaticModelRunner
 
-from . import rnn
-from .rnn import *
-
 from . import amp
 from .amp import *
 
@@ -60,5 +57,4 @@
 __all__ += checkpoint.__all__
 __all__ += learning_rate_scheduler.__all__
 __all__ += io.__all__
-__all__ += rnn.__all__
 __all__ += amp.__all__