sc a11y: Return concrete type in ScAccessibleDocument::GetAccessibleSpreadsheet

Change-Id: I11d00468deff9438038eb8d66208a8772ccdf6fe
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/210604
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>
Tested-by: Jenkins

sc/source/ui/Accessibility/AccessibleDocument.cxx

@@ -1990,8 +1990,7 @@ SCTAB ScAccessibleDocument::getVisibleTable() const
     return nVisibleTable;
 }
 
-uno::Reference < XAccessible >
-    ScAccessibleDocument::GetAccessibleSpreadsheet()
+rtl::Reference<ScAccessibleSpreadsheet> ScAccessibleDocument::GetAccessibleSpreadsheet()
 {
     if (!mpAccessibleSpreadsheet.is() && mpViewShell)
     {

sc/source/ui/inc/AccessibleDocument.hxx

@@ -160,8 +160,7 @@ public:
 
     rtl::Reference<utl::AccessibleRelationSetHelper> GetRelationSet(const ScAddress* pAddress) const;
 
-    css::uno::Reference< css::accessibility::XAccessible >
-        GetAccessibleSpreadsheet();
+    rtl::Reference<ScAccessibleSpreadsheet> GetAccessibleSpreadsheet();
 
 protected:
     virtual std::unordered_map<OUString, OUString> implGetExtendedAttributes() override;