Remove unused method.

Change-Id: Idc7919f04898b0298d6448d2dd84222b211cf5db
Reviewed-on: https://gerrit.libreoffice.org/46659Reviewed-by: Kohei Yoshida <libreoffice@kohei.us>
Tested-by: Kohei Yoshida <libreoffice@kohei.us>

sc/inc/document.hxx

@@ -870,7 +870,6 @@ public:
                                             bool bNamesValid = false );
     SC_DLLPUBLIC bool           DeleteTabs( SCTAB nTab, SCTAB nSheets );
     SC_DLLPUBLIC bool           DeleteTab( SCTAB nTab );
-    SC_DLLPUBLIC void           ClearTabs();
     SC_DLLPUBLIC bool           RenameTab( SCTAB nTab, const OUString& rName,
                                            bool bExternalDocument = false );
     bool                        MoveTab( SCTAB nOldPos, SCTAB nNewPos, ScProgress* pProgress = nullptr );

sc/source/core/data/document.cxx

@@ -783,15 +783,6 @@ bool ScDocument::DeleteTab( SCTAB nTab )
     return bValid;
 }
 
-void ScDocument::ClearTabs()
-{
-    for (auto& it: maTabs)
-    {
-        delete it;
-    }
-    maTabs.clear();
-}
-
 bool ScDocument::DeleteTabs( SCTAB nTab, SCTAB nSheets )
 {
     bool bValid = false;