umbrello/import_rose.cpp followup to commit c7fdfefc :

- In function loadFromMDL, after loop over stream.readLine() do not
  set C++ as the code generator if progLang is `Reserved' and no
  code generator is set.
  Reason: progLang value Reserved indicates that the Rose "language"
  attribute was found to be "Analysis" which corresponds to the UML
  primitive types.

CCBUG: 81364