fix: swap names of Dyadic.not_lt and Dyadic.not_le

[plp127]

This PR swaps the names of Dyadic.not_lt and Dyadic.not_le, so that Dyadic.not_lt reads ¬x < y ↔ y ≤ x and Dyadic.not_le reads ¬x ≤ y ↔ y < x. This is consistent with the corresponding lemmas for Nat, Int, Rat, and with _root_.not_lt and _root_.not_le in mathlib.

[mathlib-lean-pr-testing]

Mathlib CI status (docs):

• ❗ Batteries/Mathlib CI will not be attempted unless your PR branches off the nightly-with-mathlib branch. Try git rebase f6c7d68c7fc27e3b60585f30740c7d141d3c5b36 --onto 16e77c407779fde9a649adf3478204d1915371a3. You can force Mathlib CI using the force-mathlib-ci label. (2026-08-22 02:08:26)

[leanprover-bot]

Reference manual CI status:

• ❗ Reference manual CI will not be attempted unless your PR branches off the nightly-with-manual branch. Try git rebase f6c7d68c7fc27e3b60585f30740c7d141d3c5b36 --onto 16e77c407779fde9a649adf3478204d1915371a3. You can force reference manual CI using the force-manual-ci label. (2026-08-22 02:08:28)