ctests: run only pdf4_systemF for ja knitr/sweave

ctests: run only pdf4_systemF for ja knitr/sweave

The "bxjsarticle" class only supports export with XeLaTeX and system
fonts.

This commit uses the new exclusion functionality introduced at
10cd5dd2.

The following tests are now ignored:

  export/examples/ja/knitr_dvi
  export/examples/ja/knitr_pdf
  export/examples/ja/knitr_pdf3
  export/examples/ja/sweave_dvi
  export/examples/ja/sweave_pdf
  export/examples/ja/sweave_pdf3

The following tests are no longer ignored:

  export/examples/ja/knitr_pdf4_systemF
  export/examples/ja/sweave_pdf4_systemF