math/nlopt: Fix build by removing unneeded patch

After [1], files/CMakeLists.txt is not necessary any more.
Fix build by removing this file.

[1] https://github.com/stevengj/nlopt/commit/a5426ead8d8478c46201c21860e789e47f15c5a3

MFH: 2026Q1
(cherry picked from commit 66661b5c15b7095b5ab6af5dd0a82b9d8a2d4744)