Replace tox testenv deps with extras, to use test dependencies from setup.py

Author: davidthomas426

tox.ini

@@ -55,23 +55,7 @@ passenv =
 commands =
     coverage run --rcfile .coveragerc --source sagemaker_pytorch_serving_container -m pytest {posargs}
     {env:IGNORE_COVERAGE:} coverage report --fail-under=90 --include *sagemaker_pytorch_serving_container*
-
-deps =
-    coverage
-    pytest
-    pytest-cov
-    pytest-xdist
-    mock
-    requests == 2.20.0
-    urllib3 < 1.23, >= 1.21
-    sagemaker
-    torch
-    torchvision
-    retrying
-    six
-    future
-    pyyaml
-    protobuf == 3.19.6
+extras = test
 
 [testenv:flake8]
 basepython = python3.8