revset: cosmetic changes in spanset range comparison
We use the python syntax for range comparison: `a < x < c`. This is shorter,
more readable and less error prone. This comparison escaped the cleanup make in
e2031c8ca4f8
revset: drop spanset._contained
All its users inlined it for performance reasons.
(See
1d7a2771aa36 and
e2031c8ca4f8)