update PLDI14-List-of-Theorems.agda for consistency with #4

Camera-ready version inserts a "lemma 2.5", which means math items
2.5--2.9 should be renumbered 2.6--2.10.

Relevant commits:
23339dd5a9e56c3c31d42252c4020b716ec77725
0c1e97fbf3b62bddf23559545a4c801b4189cb29