Always show UTC tz as a choice

So, for years I never knew why my installs never showed UTC as a selection I could choose. Then I would go back and change the time zone after the install. Not any kind of problem in particular, but annoying.

Proof: https://imgur.com/a/L8y3af9

The logic used to conditionally show the UTC timezone as a choice is concise and works as intended as I found it. I plain don't like what it does. It seems to hide the UTC time zone from people in order not to bombard them with one more choice in a list of choices that number at less than a dozen-- even people that wish UTC were a choice.

You guys run the show, you can compare my deleting the conditional to the base code I changed.

The biggest worry I have is that the original code changes a variable called priority to specifically either medium or high by the end of the script. I am setting priority to whatever the priority was when the script started that the user finagled at the beginning of the install.

...I am willing to reinstate a conditional to limit the priority variable to the same pair of outcomes. But, my limited view of how this all actually works has me maybe stopping at a better place. ...Or possibly the install is more fragile than I imagine and priority="$RET" sets the variable to 'low' and everything down the line breaks.

Happy to jump through whatever hoops I missed in this submission.