Alibi explainer image broken due to numba 0.54

[RafalSkolasinski]

Describe the bug

The 1.11.0-dev image of alibiexplainer has been broken due to recent numba 0.54 release that forced newer numpy. See more SeldonIO/alibi#466

This resulted in following error.

docker run --rm -it seldonio/alibiexplainer:1.11.0-dev
2021-08-25 10:03:33.336802: W tensorflow/stream_executor/platform/default/dso_loader.cc:64] Could not load dynamic library 'libcudart.so.11.0'; dlerror: libcudart.so.11.0: cannot open shared object file: No such file or directory
2021-08-25 10:03:33.336827: I tensorflow/stream_executor/cuda/cudart_stub.cc:29] Ignore above cudart dlerror if you do not have a GPU set up on your machine.
/opt/conda/lib/python3.7/site-packages/ray/autoscaler/_private/cli_logger.py:61: FutureWarning: Not all Ray CLI dependencies were found. In Ray 1.4+, the Ray CLI, autoscaler, and dashboard will only be usable via `pip install 'ray[default]'`. Please update your install command.
  "update your install command.", FutureWarning)
RuntimeError: module compiled against API version 0xe but this version of numpy is 0xd
Traceback (most recent call last):
  File "/opt/conda/lib/python3.7/runpy.py", line 183, in _run_module_as_main
    mod_name, mod_spec, code = _get_module_details(mod_name, _Error)
  File "/opt/conda/lib/python3.7/runpy.py", line 142, in _get_module_details
    return _get_module_details(pkg_main_name, error)
  File "/opt/conda/lib/python3.7/runpy.py", line 109, in _get_module_details
    __import__(pkg_name)
  File "/microservice/alibiexplainer/__init__.py", line 1, in <module>
    from .explainer import AlibiExplainer, Protocol
  File "/microservice/alibiexplainer/explainer.py", line 28, in <module>
    from alibiexplainer.kernel_shap import KernelShap
  File "/microservice/alibiexplainer/kernel_shap.py", line 12, in <module>
    class KernelShap(ExplainerWrapper):
  File "/microservice/alibiexplainer/kernel_shap.py", line 16, in KernelShap
    explainer: Optional[alibi.explainers.KernelShap],
AttributeError: module 'alibi.explainers' has no attribute 'KernelShap'