Table title always align left in issue description

Summary

The title cell in table has always align left, but can be align right/center in table body and also in markdown

Steps to reproduce

1. Open or create a project
2. Enter project issues list
3. Create a issue
4. Enter code into Description
5. View Preview

Demo Code

| Default Header | Left Align | Right Align | Center Align |
| --- | :-- | --: | :-: |
| xxxxxxxxxxxxxxxxxx | xxxxxxxxxxxxxxxxxx | xxxxxxxxxxxxxxxxxx | xxxxxxxxxxxxxxxxxx |
| xxx | xxx | xxx | xxx |

Example Project

fenyuluoshang/demoproject#1

What is the current bug behavior?

By Demo Code

What is the expected correct behavior?

Relevant logs and/or screenshots

Output of checks

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