Removed versions 7.0.x of Exasol database

[ckunki]

Closes #368

All Submissions:

• [x] Is the title of the Pull Request correct?
• [x] Is the title of the corresponding issue correct?
• [x] Have you updated the changelog?
• [x] Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• [x] Are you mentioning the issue which this PullRequest fixes ("Fixes...")
• [ ] Before you merge don't forget to run all tests for all Exasol version, by adding [run all tests] to the commit message
• [x] Are the CLI usage examples up to date?

[ckunki]

Is it necessary to remove 7.0.x from the github workflow?

The github workflow examines the files and symlinks in folder docker_db_config_template/. But while writing this I remembered that ITDE creates a copy of each template / symlink. And I forgot to delete these copies. So please review again. 🙂