Correct and reenable SmNodeToTextVisitor's test for RSUP

See 44a3a345 about why ^ is chosen.

Change-Id: I05cda4d69eaa1757a95c06c199e09d9c67f47832
Reviewed-on: https://gerrit.libreoffice.org/13037Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

starmath/qa/cppunit/test_nodetotextvisitors.cxx

@@ -573,8 +573,8 @@ void Test::testBinHorInSubSup()
     aCursor.InsertElement(PlusElement);
     aCursor.InsertText("d");
 
-//FIXME    OUString sExpected = " { a rsup { b + c } + d } ";
-//FIXME    CPPUNIT_ASSERT_EQUAL_MESSAGE("BinHor in SubSup", sExpected, xDocShRef->GetText());
+    OUString sExpected = " { a ^ { b + c } + d } ";
+    CPPUNIT_ASSERT_EQUAL_MESSAGE("BinHor in SubSup", sExpected, xDocShRef->GetText());
 
     delete pTree;
 }