more tightened spec file produced by mageia cpanplus backend

cpanplus::dist::mageia 1.111720 has just been released, with 2 changes:

• no more %defattr definition
• no more default %clean section

indeed, rpm will handle those automatically, as dexter mentioned (cf here and here). this way, we'll have spec files a bit more tightened, which is always better from a maintainer pov.