Revert "Upgrade Django to 1.11.15 in base.in as well"
Revert "Upgrade Django to 1.11.15 in base.in as well"

This reverts commit 63ce8a7215a33b3054ac4c9f36b98baf110b9657.

appsembler/edx-platform,appsembler/edx-platform,appsembler/edx-platform,appsembler/edx-platform