Don't nest double quotes in tuiterm.exp

I found a line in tuiterm.exp that causes Emacs paren-matching to go
awry.  This patch fixes the problem by changing some apparent nested
double quotes (which I think isn't really possible in Tcl but this
seems to be the intent) to be more correct; which fixes the Emacs
issue as well.

Approved-By: Tom de Vries <tdevries@suse.de>