Please lower the recommend for apt-xapian-index to suggest

Binary package hint: synaptic

apt-xapian-index is a recommend of synaptic, and it's installed by default. But, on some systems, apt-xapian-index uses too many ressources and make system very slow (see bug 594820 and bug 769215 for example).

Considering that synaptic is a good alternative to software-center, especially on system which can't run it smoothly, adding apt-xapian-index make synaptic less interesting. Also, apt-xapian-index only adds the quick search feature, which is partly covered by the classical search.

Finally, it's a problem for Lubuntu, which especially target low hardwares, and which use synaptic as a packages manager because Software-center is too heavy for some of Lubuntu's targets.