Remove all used release notes for 6.11.0

[thomashampson]

Description of work

Removed all used release notes as per instruction in the final bullet point here

There is no associated issue.

To test:

Make sure the correct files are removed

This does not require release notes because it is release notes cleanup

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Reviewer

Please comment on the points listed below (full description).
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Code Review

• Is the code of an acceptable quality?
• Does the code conform to the coding standards?
• Are the unit tests small and test the class in isolation?
• If there is GUI work does it follow the GUI standards?
• If there are changes in the release notes then do they describe the changes appropriately?
• Do the release notes conform to the release notes guide?

Functional Tests

• Do changes function as described? Add comments below that describe the tests performed?
• Do the changes handle unexpected situations, e.g. bad input?
• Has the relevant (user and developer) documentation been added/updated?

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Gatekeeper

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[GuiMacielPereira]

Correctly removed .gitkeep and .rst files 👍