[6.0] Remove deprecated strings

[brianteeman]

This PR removes several unused strings that had already been marked for removal in 6.0

Code review only

Link to documentations

Please select:

• Documentation link for docs.joomla.org:

• No documentation changes for docs.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed

[exlemor]

I have tested this item ✅ successfully on 357e93f

I have tested this successfully and confirmed those lines are gone with the PR active.

Thanks Brian!

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[QuyTon]

I have tested this item ✅ successfully on 357e93f

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[QuyTon]

RTC

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[softforge]

Thanks @brianteeman and testers