dms: disable open button in PDF viewer

It does not make any sense to open PDF files from this gadget.

Also remove duplicate line with documentProperties
10 jobs for feat/editors in 0 seconds (queued for 1 second)
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-TestRunner1

08:28:15

passed ERP5.PerformanceTest-TestRunner1

02:58:59

failed ERP5.UnitTest-TestRunner1

09:05:42

passed ERP5.CodingStyleTest-TestRunner1

00:52:40

passed ERP5.PerformanceTest-TestRunner1

00:26:45

failed ERP5.UnitTest-TestRunner1

02:34:13

canceled ERP5.UnitTest-TestRunner1

failed ERP5.UnitTest-TestRunner1

01:42:08

canceled ERP5.UnitTest-TestRunner1

failed ERP5.UnitTest-TestRunner1

01:50:47