Let pylint validate the import order

Since the plugin pylint-django is installed, pylint is aware of
Django's recommended import order. Remove flake8's plugin that
was redundant (and following different rules).

Change-Id: I65c63a412a15e30df7c7fa431a9088e1b820d24d
diff --git a/requirements-dev-flake8.txt b/requirements-dev-flake8.txt
index 5138cfe..c10fd55 100644
--- a/requirements-dev-flake8.txt
+++ b/requirements-dev-flake8.txt
@@ -1,5 +1,4 @@
 flake8 >= 3.5.0, < 3.6.0
 flake8-colors
 flake8-docstrings
-flake8-import-order
 pep8-naming
diff --git a/tox.ini b/tox.ini
index 9f82eb6..c0f3881 100644
--- a/tox.ini
+++ b/tox.ini
@@ -40,5 +40,4 @@
 # Flake8 configuration
 [flake8]
 format = ${cyan}%(path)s${reset}:${yellow_bold}%(row)d${reset}:${green_bold}%(col)d${reset}: ${red_bold}%(code)s${reset} %(text)s
-import-order-style = google
 max-complexity = 10