util: remove unneeded #include in virrandom.c

util: remove unneeded #include in virrandom.c

Commit 7c90026 added #include "conf/domain_conf.h" to
util/virrandom.c. Fortunately it didn't actually use anything from
domain_conf.h, since as far as I'm aware, files in util aren't allowed
to reference anything in conf (although the opposite is allowed). So
this #include is unnecessary.

I verified it still compiles with the line removed, but have placed a
one day moratorium on me doing any "trivial rule" pushes, so will
wait for someone else to verify/ACK before pushing.