resize-mini-windows hardcoded to grow-only

[zenspider]

In 08b165c, despite the commit message, it sets resize-mini-windows to 'grow-only. This prevents any other value like t which would allow the minibuffer to shrink to size. Since the default for that value is already 'grow-only, maybe remove it so the user's setting can take effect? Otherwise, maybe extract it to a custom variable so it can be tweaked by the user.

A value of nil means don't automatically resize mini-windows.
A value of t means resize them to fit the text displayed in them.
A value of grow-only, the default, means let mini-windows grow only;
they return to their normal size when the minibuffer is closed, or the
echo area becomes empty.

Personally, I don't like the minibuffer starting w/ > max selections to whittle it down to 3 but still show it in the full sized display. I want it to shrink down to the number I've reduced it to whenever possible.