Drop FFTW-3.3.3-ictce-5.3.0-single.eb etc


Hi,

after providing "jumbo FFTWs" a couple releases ago, I understand the following ones should be withdrawn,
to promote using the generic versions (and avoid other module conflicts down the road):
* easybuild/easyconfigs/f/FFTW/FFTW-3.3.3-ictce-5.3.0-single.eb [DONE]
* easybuild/easyconfigs/f/FFTW/FFTW-3.3.3-ictce-4.1.13-single.eb
* easybuild/easyconfigs/f/FFTW/FFTW-3.3.3-iomkl-4.6.13-single.eb

The 1st case I dropped already since I know I added it in inadvertently, in a massive step providing for ictce/5.3.0
and from what I know it is not used by anybody (jumbo FFTW does the job right).

As regards the other two, I suggest that Kenneth makes a comment (coming in from commit a847b76e). From what I see, they are not used either...