Remove broken leftover assertion.

I removed the 'pplstmt' argument in commit 413cb592, because all the
callers passed NULL. But missed this assertion that still referenced it.
Remove it, too.

Per off-list report by Haisheng Yuan.

src/backend/gpopt/translate/CTranslatorScalarToDXL.cpp

@@ -82,7 +82,6 @@ CTranslatorScalarToDXL::CTranslatorScalarToDXL
 	m_phmulCTEEntries(phmulCTEEntries),
 	m_pdrgpdxlnCTE(pdrgpdxlnCTE)
 {
-	GPOS_ASSERT_IMP(!fQuery, pplstmt);
 }
 
 //---------------------------------------------------------------------------