Remove unnecessary MANIFEST.in (#439)

* This MANIFEST.in unnecessary with setuptools_scm

https://github.com/pypa/setuptools_scm/blob/master/README.rst#file-finders-hook-makes-most-of-manifestin-unnecessary

* No manifest to check

MANIFEST.in

@@ -1,6 +0,0 @@
-recursive-include docs *
-recursive-include tests *
-include pyproject.toml pytest.ini tox.ini .coveragerc .pre-commit-config.yaml *.md LICENSE AUTHORS
-prune docs/_build
-prune *.pyc
-prune __pycache__

tox.ini

@@ -17,7 +17,6 @@ commands =
 
 [testenv:lint]
 deps =
-    check-manifest
     flake8
     # flake8-black
     pre-commit
@@ -25,7 +24,6 @@ deps =
 commands =
     # flake8 src/tablib tests/
     pre-commit run --all-files
-    check-manifest -v
     python setup.py sdist
     twine check dist/*
 skip_install = true