updated the button component to better render aria-label

[alexwbbr]

Fixes how the aria label was being rendered by the button component https://github.com/Capgemini/dcx-react-library/issues/618

• The aria-label should default to the label if not specified as voice activation users won't know what type of button it is or that it has "-button" added afterwards.
• The aria-label attribute should always be rendered if a value is given, it doesn't make sense to hide it if the label property is being used.

[codecov-commenter]

Codecov Report

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

Project coverage is 100.00%. Comparing base (be71118) to head (3c17b65).

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## epic/accessibility-issues #619 +/- ## =========================================================== Coverage 100.00% 100.00% =========================================================== Files 85 85 Lines 1512 1511 -1 Branches 527 526 -1 =========================================================== - Hits 1512 1511 -1 ```

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