SwContentArr: fix STL conversion:

It appears that the operator== for SwContent always returns false,
so 81181891 changed the semantics;
use o3tl::find_partialorder_ptrequals to fix it.

Change-Id: Ib4f040f03a9eaeec9a2973f5a93a22a387232017

sw/source/ui/utlui/content.cxx

@@ -105,7 +105,9 @@ using namespace ::com::sun::star::container;
 #define NAVI_BOOKMARK_DELIM     (sal_Unicode)1
 
 class SwContentArr
-    : public o3tl::sorted_vector<SwContent*, o3tl::less_ptr_to<SwContent> >
+    : public o3tl::sorted_vector<SwContent*, o3tl::less_ptr_to<SwContent>,
+                o3tl::find_partialorder_ptrequals<SwContent*,
+                    o3tl::less_ptr_to<SwContent> > >
 {
 public:
     ~SwContentArr() { DeleteAndDestroyAll(); }