Revert "tdf#95687: Wrong function names in Formula Writer are considered as SUM"

This reverts commit 010ed5e6.
The fix was too naive and generated a problem during PythonTest_sw_python with set_expression test

sw/source/core/bastyp/calc.cxx

@@ -713,7 +713,7 @@ SwCalcOper SwCalc::GetToken()
             }
             aVarName = aName;
             eCurrOper = CALC_NAME;
-            bSetError = true;
+            bSetError = false;
         }
         else if ( aRes.TokenType & KParseType::DOUBLE_QUOTE_STRING )
         {