Fix imports following Keras code reorganization

[tsokk]

Following installation instructions and running tests as indicated leads to two errors due to reorganized Keras code. Note that there is a related approved pull request that fixes one of the problems. This pull request patches both of the two failing modules.

platform linux -- Python 3.9.7, pytest-6.2.5, py-1.10.0, pluggy-1.0.0
rootdir: /home/teemu/aima-python, configfile: pytest.ini
plugins: cov-3.0.0
collected 419 items                                                           

tests/test_agents.py ................                                   [  3%]
tests/test_agents4e.py ................                                 [  7%]
tests/test_csp.py .........................................             [ 17%]
tests/test_deep_learning4e.py ...F                                      [ 18%]
tests/test_games.py ...                                                 [ 19%]
tests/test_games4e.py ....                                              [ 20%]
tests/test_knowledge.py ...........                                     [ 22%]
tests/test_learning.py ...............                                  [ 26%]
tests/test_learning4e.py .............                                  [ 29%]
tests/test_logic.py ......................................              [ 38%]
tests/test_logic4e.py ....................................              [ 47%]
tests/test_mdp.py ......                                                [ 48%]
tests/test_mdp4e.py ......                                              [ 49%]
tests/test_nlp.py ....................                                  [ 54%]
tests/test_nlp4e.py ............                                        [ 57%]
tests/test_perception4e.py .......F.                                    [ 59%]
tests/test_planning.py .....................................            [ 68%]
tests/test_probabilistic_learning.py .                                  [ 68%]
tests/test_probability.py ........................                      [ 74%]
tests/test_probability4e.py ......................                      [ 79%]
tests/test_reinforcement_learning.py ....                               [ 80%]
tests/test_reinforcement_learning4e.py ....                             [ 81%]
tests/test_search.py ..........................                         [ 87%]
tests/test_text.py ...............                                      [ 91%]
tests/test_utils.py ....................................                [100%]