chore(Topology/Order): fix name of nhdsLT lemma

[b-mehta]

The dual version of this was renamed over a year and a half ago, and it looks like this one was missed. In particular, all lemmas in mathlib about 𝓝[<] are named nhdsLT with this one as the sole exception, and we choose the new name to match the dual nhdsGT_neBot_of_exists_gt.
Note that the statement itself appears different, but is definitionally equal to the old one, and again matches the dual.

---

[github-actions]

PR summary 7ee74e7d3f

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

---

Declarations diff

+ nhdsLT_neBot_of_exists_lt

You can run this locally as follows

## summary with just the declaration names:
./scripts/declarations_diff.sh <optional_commit>

## more verbose report:
./scripts/declarations_diff.sh long <optional_commit>

The doc-module for script/declarations_diff.sh contains some details about this script.

---

No changes to technical debt.

You can run this locally as

./scripts/technical-debt-metrics.sh pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).