fix image paths in moved GitLab auth guide

Signed-off-by: mcnesium <[email protected]>

Author: mcnesium

docs/guides/auth/gitlab-self-hosted.md

@@ -7,12 +7,12 @@
 2. Navigate to the application management page at `https://your.gitlab.domain/admin/applications` (admin permissions required)
 3. Click **New application** to create a new application and fill out the registration form:
 
-![New GitLab application](images/auth/gitlab-new-application.png)
+![New GitLab application](../images/auth/gitlab-new-application.png)
 
 4. Click **Submit**
 5. In the list of applications select **HackMD**. Leave that site open to copy the application ID and secret in the next step.
 
-![Application: HackMD](images/auth/gitlab-application-details.png)
+![Application: HackMD](../images/auth/gitlab-application-details.png)
 
 
 6. In the `docker-compose.yml` add the following environment variables to `app:` `environment:`
@@ -29,4 +29,4 @@
 7. Run `docker-compose up -d` to apply your settings.
 8. Sign in to your HackMD using your GitLab ID:
 
-![Sign in via GitLab](images/auth/gitlab-sign-in.png)
+![Sign in via GitLab](../images/auth/gitlab-sign-in.png)