Update readme to remove mention of DockerHub registry

[rv0lt]

Read this before submitting the PR

1. Always create a Draft PR first
2. Go through sections 1-5 below, fill them in and check all the boxes
3. Make sure that the branch is updated; if there's an "Update branch" button at the bottom of the PR, rebase or update branch.
4. When all boxes are checked, information is filled in, and the branch is updated: mark as Ready For Review and tag reviewers (top right)
5. Once there is a submitted review, implement the suggestions (if reasonable, otherwise discuss) and request an new review.

If there is a field which you are unsure about, enter the edit mode of this description or go to the PR template; There are invisible comments providing descriptions which may be of help.

1. Description / Summary

Remove mention of DockerHub registry

2. Jira task / GitHub issue

Link to the github issue or add the Jira task ID here.

3. Type of change

What type of change(s) does the PR contain?

Check the relevant boxes below. For an explanation of the different sections, enter edit mode of this PR description template.

• [] New feature
  • [ ] Breaking: Why / How? Add info here.
  • [ ] Non-breaking
• [ ] Database change: Remember the to include a new migration version, or explain here why it's not needed.
• [ ] Bug fix
• [ ] Security Alert fix
  • [ ] Package update
  • [ ] Major version update
• [X] Documentation
• [ ] Workflow
• [ ] Tests only

4. Additional information

• [X] Sprintlog
• [ ] Blocking PRs
  • [ ] Merged
• [ ] PR to master branch: _If checked, read the release instructions
  • [ ] I have followed steps 1-8.

5. Actions / Scans

Check the boxes when the specified checks have passed.

For information on what the different checks do and how to fix it if they're failing, enter edit mode of this description or go to the PR template.

• [x] Black
• [x] Prettier
• [x] Yamllint
• [x] Tests
• [x] CodeQL
• [x] Trivy
• [x] Snyk

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 92.52%. Comparing base (7f3414d) to head (83a2df4). Report is 10 commits behind head on dev.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## dev #1558 +/- ## ======================================= Coverage 92.52% 92.52% ======================================= Files 29 29 Lines 4868 4868 ======================================= Hits 4504 4504 Misses 364 364 ```

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