Remove unneeded `%I`s.

exercises/ex_02_sumlist.v

exercises/ex_03_spinlock.v

exercises/ex_04_parallel_add.v

exercises/ex_05_parallel_add_mul.v

solutions/ex_02_sumlist.v

solutions/ex_03_spinlock.v

solutions/ex_04_parallel_add.v

solutions/ex_05_parallel_add_mul.v

talks/demo/demo.v