Resolves: tdf#121940 mnemonic ends up in tooltip text

Change-Id: Ic698f23e71dbc613db2acf884fdefdeab06fde0f
Reviewed-on: https://gerrit.libreoffice.org/65968
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

sw/source/uibase/wrtsh/wrtundo.cxx

@@ -25,6 +25,7 @@
 #include <swdtflvr.hxx>
 #include <svtools/svtresid.hxx>
 #include <svtools/strings.hrc>
+#include <vcl/mnemonic.hxx>
 
 // Undo ends all modes. If a selection is emerged by the Undo,
 // this must be considered for further action.
@@ -108,7 +109,7 @@ OUString SwWrtShell::GetDoString( DoType eDoType ) const
     default:;//prevent warning
     }
 
-    return SvtResId(pResStr) + aUndoStr;
+    return MnemonicGenerator::EraseAllMnemonicChars(SvtResId(pResStr)) + aUndoStr;
 }
 
 void SwWrtShell::GetDoStrings( DoType eDoType, SfxStringListItem& rStrs ) const