Update section name Monotonic to Monotonicity in auto-increment.md (#4028)
Update section name Monotonic to Monotonicity in auto-increment.md (#4028)

* Update auto-increment.md

The previous section name is Uniqueness, a noun, while the section name being updated in this PR was Monotonic, an adjective.

* trigger CI

* trigger CI

Co-authored-by: TomShawn <3d0966147538bc5ab020e8dffa2c0b746f9728a6@users.noreply.github.com>
pingcap/docs,pingcap/docs,pingcap/docs