stoc: avoid -Werror=deprecated-copy (GCC trunk towards GCC 9)

...by removing explicitly user-provided functions that do the same as their
implicitly-defined counterparts, but may prevent implicitly declared copy
functions from being defined as non-deleted in the future

Change-Id: Iacfdd89ca6ca3af19a56cd26721e1ce2d47c49fa
Reviewed-on: https://gerrit.libreoffice.org/58055
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

stoc/source/security/permissions.h

@@ -67,9 +67,6 @@ class PermissionCollection
 public:
     PermissionCollection()
         {}
-    PermissionCollection( PermissionCollection const & collection )
-        : m_head( collection.m_head )
-        {}
     explicit PermissionCollection( ::rtl::Reference< Permission > const & single )
         : m_head( single )
         {}