rcutorture: Remove obsolete SRCU-C.boot

Classic SRCU is no more, so this commit removes the corresponding
rcutorture boot-parameters file.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

tools/testing/selftests/rcutorture/configs/rcu/SRCU-C.boot

-rcutorture.torture_type=srcud