Remove SESSION_COOKIE_HTTPONLY from local_settings

After a discussion with the Horizon developers, remove
SESSION_COOKIE_HTTPONLY from local settings. This is already the
default in Horizon and need not be set in local_settings. See #1333407.

Change-Id: If6c63d6e03b2a16383bd209283b129c20ca95899
Merge "Remove SESSION_COOKIE_HTTPONLY from local_settings"