GitLab Registry Scan not working

**Describe the bug**
When adding a GitLab registry, it does not detect the published containers images.

**To Reproduce**
Steps to reproduce the behavior:
1. Go to 'Registries'
2. Click on 'GitLab'
3. Click on '+Add Registry'
4. Enter the registry's information
a. Registry Name: GitLab
b. GitLab Registry Server URL: https://gitlab.domain.local
c. GitLab Registry URL: gitlab.domain.local
d. Token: xxxxxxxxxxxxxxxxxx
6. Click 'Save Credentials'
7. The page shows a new entry for the GitLab registry but no images detected

**Expected behavior**
After adding the GitLab registry, it should show the Total Images being more than 0.

**Screenshots**

**Components/Services affected**

- [ ] UI/Frontend
- [ ] API/Backend
- [ ] Registry Scanner

**Additional context**
Environment Information:
|Component | Version|
|---|---|
| Deepfence | 1.4.0 |
| Docker host OS | Ubuntu 20.04.4 LTS |
| Docker | 20.10.12 |
| GitLab | 15.0.5-ee |