Adress #694

Changes proposed in this pull request:

• Updated release protocol with info on credentials for test.pypi.org (step 9) and added "Fixed" to unreleased section of changelog.md in release protocol

The following steps were realized, as well (if applies):

• ❌ Use in-line comments to explain your code
• ❌ Write docstrings to your code (example docstring)
• ❌ For new functionalities: Explain in readthedocs
• ❌ Write test(s) for your new patch of code (pytests, assertion debug messages)
• Update the CHANGELOG.md
• ❌ Apply black (black . --exclude docs/)
• ❌ Check if benchmark tests pass locally (EXECUTE_TESTS_ON=master pytest)

Please mark above checkboxes as following:

• Open
• Done

❌ Check not applicable to this PR

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