Trigger autosize update after template selection

## What does this MR do?

Triggers an autosize update after selecting an issue template.

The autosize plugin doesn't react to value changes and therefore doesn't automatically update when the user selects the template. This merge request adds it so that it detects if the editor the template selector is a jQuery object (not Ace editor) & then triggers the autosize event to allow the user to scroll the textarea.

## Screenshots (if relevant)

![resize](/uploads/1ab04b4202309b13f1178e04c0953112/resize.gif)

## What are the relevant issue numbers?

Closes #21982

See merge request !6282