[4.0] Add period

[Quy]

Summary of Changes

Add period to the alert message.

Testing Instructions

Code review.

or

Go to System > Update > Extensions
Click Clear Cache button.
See message.

[brianteeman]

I have tested this item ✅ successfully on ffd564a

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/33132.}

[ChristineWk]

I have tested this item ✅ successfully on ffd564a

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/33132.}

[Quy]

RTC

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/33132.}

[Quy]

Thank you!