update www/seahub to 6.0.7

Changes: https://seacloud.cc/group/3/wiki/server-changelog

 - [fix] Fix generating of password protected link in file view page
 - [fix] Fix .jpg/.JPG image display in IE10
 - Export quota usage in export Excel in user list admin page
 - [fix] Fix admin can't delete broken libraries
 - Add "back to previous page" link in trash page, history page
 - [fix] Improve logo show in About page
 - [fix] Fix file encoding for text file editing online
 - [fix] Don't show operation buttons for broken libraries in normal users page

 PR: 216349
 Submitted by: ultima1252@gmail.com (maintainer)
 Reviewed by: matthew
 Approved by: matthew (maintainer)
 Differential Revision: https://reviews.freebsd.org/DXXXX