[flang] Minor fix to list-directed REAL output editing

[klausler]

Summary

Always emit the letter 'E' in list-directed REAL output;
the library was omitting it for exponents greater than 99,
as should be done for E and D formatting of large exponents
without an Ed exponent digit count.

[PeteSteinfeld]

All builds, tests, and looks good.

flang/runtime/edit-output.cpp

if (int ed{*edit.expoDigits}) { // Ew.dEe with e > 0
       *--exponent = '0'; // Ew.dE0 with zero-valued exponent
     }
   } else { // ensure at least two exponent digits
     while (exponent + 2 > eEnd) {
       *--exponent = '0';
     }
   }
   *--exponent = expo < 0 ? '-' : '+';
-  if (edit.expoDigits || exponent + 3 == eEnd) {
+  if (edit.expoDigits || edit.IsListDirected() || exponent + 3 == eEnd) {
     *--exponent = edit.descriptor == 'D' ? 'D' : 'E'; // not 'G'
   }
   length = eEnd - exponent;
   return exponent;
 }
 
 bool RealOutputEditingBase::EmitPrefix(
     const DataEdit &edit, std::size_t length, std::size_t width) {