[4.0] Add text muted property to show verison is not clickable

[wilsonge]

Summary of Changes

Adds a text-muted property to the version to show it's not clickable. This is an alternative PR to that in #26447

Testing Instructions

After patch Joomla version in the header of the backend is grayed out to show it's not clickable

Documentation Changes Required

None

[Quy]

I have tested this item ✅ successfully on 3abaf71

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[SharkyKZ]

I have tested this item ✅ successfully on 3abaf71

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/26734.}

[SharkyKZ]

RTC

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/26734.}

[wilsonge]

Thanks!