configure.in: remove no longer used variable

* configure.in (unexpand_shvar): remove variable which is no longer
  used since r39506.  [Bug #7959]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39514 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

configure.in

@@ -3284,7 +3284,6 @@ unexpand_shvar() {
     local var=$1 val n v expr
     shift
     test "$#" -eq 0 && return
-    quote=['']
     for n do
         eval v='"$'$n'"'
 	v="`echo \"$v\" | sed -e ['s/${[^${}"]*}/"&"/g'] -e ['s/[][$|.\\?*]/\\\\&/g']`"