Removed individual release note files 6.6

[jhaigh0]

Description of work.

Deleted the directory structure which holds the individual release note files so that just the main files are remaining.

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Reviewer

Please comment on the following (full description):

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?
• Are the release notes saved in a separate file, using Issue or PR number for file name and in the correct location?

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?

Does everything look good? Mark the review as Approve. A member of @mantidproject/gatekeepers will take care of it.

[cailafinn]

Looks good to me. Checked the docs build and look right, just to be sure, and they do. Nice work 👍

[martyngigg]

@gemmaguest @thomashampson The is has cleaned up the used release notes so the build should be ready to go?