fix(FloatingButtons): Add missing `aria-label` to NcButton components

[mejo-]

Fixes: #8031

🏁 Checklist

• [x] Code is properly formatted (npm run lint / npm run stylelint / composer run cs:check)
• [x] Sign-off message is added to all commits

[mejo-]

/backport to stable32

[codecov[bot]]

Codecov Report

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

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[max-nextcloud]

I tried to reproduce the problem in main branch but could not see the warnings so could not test this.

[susnux]

@max-nextcloud the funny thing is I did not see this in the text app but in the tables app which seems to have a text integration?

[susnux]

(anyways missing aria labels when there is no visual text are always a reason to fail WCAG so good that this is fixed now :) )

[mejo-]

/backport to stable32