Fix entity reference module security issue:
DRUPAL-SA-CONTRIB-2017-067
https://www.drupal.org/node/2902596
This patch removes the "Autocomplete widgets cannot reference a single
entity result" https://drupal.org/node/1959624#comment-8451891 - it was
merged as d8e3926 commit.
Change-Id: If5b997dac31016e8ebaf3b5b1fc0216bd456b3b0
Marton Kiss