a7a8b94c67fac3de4496e4bb57adb724d3bfaee5 Fix a few minor errors in the dseries doc. (cherry picked from commit cb0439345cc677ab83a1bbc9a2e5ec442418f515)

================================ DYNARE MAKE CHECK MATLAB RESULTS ================================ | TOTAL: 417 | PASS: 415 | FAIL: 0 | XFAIL: 2 | XPASS: 0

================================ DYNARE MAKE CHECK OCTAVE RESULTS ================================ | TOTAL: 415 | PASS: 413 | FAIL: 0 | XFAIL: 2 | XPASS: 0

A full log can be found on karaba in '/tmp/dynare-4.4-check-SimNDnEk4f.log'.