Unnecessary Include Header Removal

[kfv]

Summary

`libjail/jail.c' has included both <sys/param.h> and <sys/types.h> wherein the latter is unnecessary since it's already included by <sys/param.h>.

[dteske]

I approve of this change. But since I have not committed in a while, want to get sign-off from at least one other person.

[dteske]

@rgrimes @cem If one of you approve, I'll go ahead and usher it in

[cem]

(<sys/param.h> includes <sys/types.h>; do not include both.)

— style(9)

[kfv]

Thanks everyone.