Bug 21243: (follow-up) Remove extra '</div>' tag

Bug 21243: (follow-up) Remove extra '</div>' tag

To test:
1 - Go to Admin->Z39/SRU servers
2 - Pick a server or add one
3 - Click 'Modify' button for mappings
4 - Copy the HTML of the popup into w3c validator
https://validator.w3.org/#validate_by_input
5 - Note extra closing div
6 - Apply patch
7 - Repeat
8 - Success

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
(cherry picked from commit 10cd9ac4bdc430d29bc71299e5d9b5d3bc8b1489)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>