Search author suggestion requires minimum 3 characters

Summary

In issue index page search box, when author criteria pops up, user must enter at least three characters before any suggested users show up.

Steps to reproduce

1. Go to issues index page https://gitlab.com/gitlab-org/gitlab/issues
2. In search bar, type author: for suggestion popup
3. Type "lu" and nothing will show up
4. Type "lul" then me as a suggestion will come up

Example Project

Any project will do

What is the current bug behavior?

When typing 1 or 2 characters, author suggestion does not suggest anyone.

What is the expected correct behavior?

When typing 1 or 2 characters, author suggestion should suggest someone.

Relevant logs and/or screenshots

search_suggestion

Output of checks

This bug happens on GitLab.com

Results of GitLab environment info

Expand for output related to GitLab environment info

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:env:info)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production)

Results of GitLab application Check

Expand for output related to the GitLab application check

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)
(we will only investigate if the tests are passing)

Possible fixes

Probably due to search optimization which limits the minimum search term length.