LP1791791: Google book previews not displaying from a bib linked from a search.

LP1791791: Google book previews not displaying from a bib linked from a search.

The javascript that queries Google Books Preview looks for ISBN(s) wrapped in
a rdetail_value class.  There was a line of code in which the isbn variable
 was not enclosed in this class.  This patch just wraps that stray variable
into a <span> with the class.

To test:
0. Use the TPAC skin - this bug does not affect the Bootstrap skin
1. Perform a keyword search for an bib that should have a google book's link.
   As of March 2023, ISBN 9780786496570 has previews enabled.
2. Go to the bib display and notice that there is no link.
3. Remove the ';query=something' text from the url and notice that the
google book information displays.
4. Apply the patch.
5. Perform the same search.  The google book information should now display.

Signed-off-by: Garry Collum <gcollum@gmail.com>
Signed-off-by: Galen Charlton <gmc@equinoxOLI.org>